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BY MARK JONASSON

Dave Mack

 

Gold in the sluice.Gold. Just the word strikes up many images in the mind: gleaming bars in a vault, Old-49’ers in a rough-and-tumble boom town, a mine shaft deep in the earth or prospectors squatting beside a mountain stream oscillating their gold pans….

Not long ago, Tom, Randy and I developed a case of a highly-contagious and debilitating fever, gold fever. Because our vacations all coincided, we decided to spend the time prospecting. We packed up and, pans in hand, headed for the Mother Lode Country in California. Our plan consisted of searching areas of the Merced River and several forks of the American River.

Gold has been prized from antiquity because of its scarceness and its inherent qualities. These inherent qualities, like its ability to be hammered paper-thin, its ability to be drawn into hair-thin wires, its weight–19 times heavier than water, and resistance to corrosion, have made gold the most sought-after metal throughout history. As far back as 4,000 B.C. the Egyptians were fashioning artifacts from gold. Gold is the first element mentioned in the Bible (Genesis 2: 10-12). Gold played an important role in the social and religious structure of the Inca and Aztec civilizations of Latin America.

Gold in a gold panMore recently, the gold rushes beginning in the early 19th century in the southeastern United States, followed by the great California rush of 1849, and by later strikes in the Rockies and Alaska, have kept gold fever smoldering to the present day.

Part of the recurring interest in gold is the estimate that over 80 percent of all existing gold worldwide has yet to be discovered.

Because of its weight, a lot of gold takes up just a little space. For example, a cubic-foot of gold weighs more than half a ton and the gold would be worth over $7.5 million dollars!

Knowing where to look for gold is probably responsible for 97 percent of the success that a prospector experiences. There are several good books that will get beginning prospectors started right. Dave McCracken’s Gold Mining in the 21st Century is probably the best. Two other books are; Gold Digger’s Atlas by Robert Neil Jonnson, and Gold! Gold! A Beginners Handbook And Recreational Guide: How To Prospect , by Joseph F . Petralia.

The areas of greatest-known gold concentration in the United States are in the Sierra Nevada and Rocky Mountain ranges. The Klamath Range in Siskiyou County, California remains quite active for small-scale gold prospectors even to this day, especially the area surrounding Happy Camp. Sufficient concentrations of gold were also mined from 1830 to 1840 in the Appalachians, as well as the mountains of Vermont and New Hampshire, to warrant an interest, particularly at current price levels for gold.

Gold cleaned and on a scaleIn 1986, California experienced a snow pack and spring runoff that were exceptional. The flow of the American River near Auburn, California became so great that colossal cement pilings and support slabs were slapped aside by the water as if they were empty cereal boxes. Even months after the high water, evidence of the tremendous force could still be seen on and around the American River Bridge near Auburn. The unusually high water turned many streams and rivers into raging torrents. This forced more gold out of hiding, and made for a tremendous prospecting season. Even so, reading the stream and bench placers properly can mean the difference between mediocre and memorable prospecting results.

Another very large flood storm really tore up the area around Happy Camp in 1997.

In addition to choosing a potentially profitable geographic area, the prospector must also choose the correct area of a streambed to work. Gold settles almost immediately where water-speed slows down: behind boulders, at the bottom of a riffle section and on the inside of river and stream bends. Even though stream placers can be productive, do not overlook bench placers. During spring, high-water bench placers are often “restocked.”

Basic prospecting gear can be purchased for less than a tank of gas, unless you are riding a motorcycle, and should last indefinitely. Useful tools for prospecting, some of which you may already have at home, include: a bucket, coffee can, garden trowel, tweezers, old spoon, whisk broom, pry bar, magnet, a sifting device and shovel. You will need one small vial or zip-lock baggie to store the gold you find, a crevice tool, and of course a gold pan. These last items may be purchased at a rock, prospecting shop or from the Internet.

I suggest you purchase a high-impact plastic gold pan; it is lighter, very durable, and the black, blue or green color allows greater contrast of the gold against the darker background. Most plastic pans have traps and riffles molded into them to aid in gold recovery.

The mornings and evenings of our prospecting trip were cool and the warmth of the campfire felt comforting; but the days, and particularly the afternoons, were blistering-hot. Because we were in close proximity to water, coping with the heat was relatively easy. Not only did we jump in every half hour or so to cool off, but we soon began prospecting entirely within the river. It is amazing how much gold you can find just swimming around with mask and snorkel, while fanning light gravel from cracks in the bedrock!

During the first several days of our gold trip, one participant developed such an increasingly acute gold fever; that in an effort to not waste a moment on creature comforts, he began panning in mid-stream while almost completely submerged. All prospectors in our group soon were diving down and bringing gravel up from the bottom of the river. We sat around the campfire at night just imagining how much more gold we would have recovered had we brought along a suction dredge on our venture. It was a great trip!

Prospecting is a pleasant activity for me. I often take an afternoon or weekend, and enjoy the gold I find as well as the prospecting. Gold prospecting can be done on a solo trip, a family trip or with a large group. People of all ages can prospect for gold and enjoy the search. You will enjoy prospecting, and the exercise in the out-of -doors is just an added plus.

 

By Dave McCracken

How much you need to qualify a gold deposit in advance depends upon the additional investment that will be required to gear-up for production.

Dave Mack

In placer mining, there are fundamentally two kinds of sampling:

1) Discovery: Attempting to locate a higher-grade deposit of value inside of a larger volume of lower-grade material.

2) Quantification: Extracting and analyzing smaller portions, to gain a perception of how much value exists within a larger volume.

The general concept behind sampling is to minimize investment into a specific mining property, or a particular project, until there is enough proof that a mineral deposit exists which contains enough value to justify a more substantial investment.

The kind of sampling that you should do, and how much is necessary, largely depends upon the ultimate objectives, and/or how large of an investment you will make to implement a commercial project – especially that portion of the investment which cannot be recovered and re-committed to some other project at a later time.

For example, if you are going to join The New 49’ers Prospecting Organization to gain access to 60+ miles of mineral properties in northern California, and decide to devote an extended period of time into searching for and developing high-grade gold deposits along those properties, the money you would spend outfitting yourself with a sampling dredge is something you can depreciate over the extended period. This is because the investment will not be confined to a single mining project or property. When you are done, because the dredge and gear will be accessible, you can regain some of your investment by selling the used equipment.

How much sampling would be necessary in advance of making this investment? Not so much, because most of the investment is not committed to a single mining property. Before a final decision is made, perhaps it would be worth spending a week of your time participating in a Group Mining Project, to obtain some direct exposure to the activity, and see if this is how you want to spend your time.

On the other hand, if you were considering a substantial capital investment to start up a full-scale commercial dredging program on one specific mining property out in the middle of Borneo’s rain forest, where accessibility is only available by helicopter; it would be wise to first send in a sampling-team to confirm the existence of commercial deposits that will allow you to make a reasonable return on your investment. Knowing that most of the capitalization into this kind of mining project is unlikely to be diverted to some other program at a later time, how much sampling would be enough? It should be enough to:

1) Verify that commercial deposits exist on the property; and,

2) Quantify the deposit(s) well enough to become certain that the commercial value of the project is justified.

Sampling is a careful, organized method of attempting to locate high-grade mineral deposits; and then, obtain a reasonable perception of the value they contain.

Here are a few basic sampling principles:

1) The larger the sample, the more accurately the sample results will represent the larger volume of material that has not been analyzed.

2) The more samples you take, and the closer they are together, the more accurately the average result will represent the larger volume of material that has not been analyzed.

3) To achieve an accurate result in sampling, it is vital that you thoroughly clean all of the values from sampling equipment in-between samples.

4) As mineral deposits can be found at different strata’s within a streambed, a good sampling program does not only test in different geographic locations; but also at the different layers within a streambed. This is because it can often be more commercially-productive to mine a deposit only down to a specific strata.

 

On this river in Madagascar, the gold (plentiful) was so fine, the sample material had to be dredged into a large catch basin suspended between two boats, and then processed using specialized equipment on the bank.

5) To be effective, recovery-equipment used in sampling must have the capability of concentrating the values which exist within the deposit. Where special recovery equipment is needed, and the sampling must be accomplished with portable dredging equipment, it is sometimes necessary to dredge the samples into a floating catch-container. Then the samples can be carefully processed on land.

Sizing the gold being recovered, and the gold that is not being recovered, is an important part of a sampling process.


6) Care must be taken to ensure that foreign material is not introduced into the material being sampled which can render the result inaccurate. Just as this has to do with foreign material from other geographic locations, it also has to do with material from different strata’s within the streambed, if layers are being tested independently of each other.

7) The smaller the sample being analyzed, the more the result can be thrown off by the introduction of foreign material (called “contamination.”)

8) Tailings from a sampling recovery system should be carefully analyzed to see what values are being lost; and whether steps can be taken to recover the values in a production operation.

9) Ultimately, only the values that can be recovered during production should be included in the final business projections.

10) Care must be given to measure the amount of raw volume that is excavated to extract a sample. Because the value recovered must be related back to the amount of material that was moved and/or processed to obtain the result. This relation will need to be measured against the volumes and costs associated with a potential production operation.

For example: If an average cubic meter of streambed gravel to be processed will produce $10 in gold (gold at $425/ounce), at a gross production cost of $4 per cubic meter, when a production dredge is operating at 100 cubic meters per day, you can predict a net income of $600 for each dredge participating in the program.

Sampling is generally accomplished in two steps: The first step is to locate the existence of a mineral deposit. Usually, when we use the term “preliminary sampling program,” we are talking about a project where the existence of high-grade deposits still needs to be confirmed.

The second step is to sample the deposit(s) enough to gain a perception of its value. And that’s what this article is really about; how much quantification is necessary? The answer to this question largely depends upon the additional investment that will be required to gear-up for the desired volume of production.

Where we dredge along the Klamath River in northern California, using the very same equipment and support-structure in sampling as we do in production, we do not have to do very much quantification of a deposit before launching into production. This is because just finding the high-grade is reason-enough to mine it. Although, we usually do devote several samples in an effort to find a low-grade area where we can place tailings. Then, we establish the value of the deposit as we mine it.

The reason we can do this, is that under these circumstances, there is no substantial amount of increased financial risk when we transition from sampling into production.

Local miners were recovering rich deposits in the Cambodian jungle using very primitive, low-volume methods. Here was a good place to start with a sampling dredge.

However, many situations are different from this. Some mining projects are just in the start-up phase. Some mining prospects are in remote locations. Under many circumstances, to minimize risk, it is wise to begin with portable sampling equipment to complete the preliminary sampling phase of the program.

Local miners were supporting their villages in Madagascar by digging gravel from the bottom of the river out of boats using long-handled shovels. Our sampling later proved they were digging on the strongest line of gold in the river.

In this case, the question remains how much quantification is necessary to support the evolution to the next level of operations? This will always come back to the program objectives – which often have to remain flexible, depending upon what is discovered during sampling.

Here are several different levels of quantification:

1) Doing enough additional samples to prove that a high-grade deposit justifies bringing in a larger-sized suction dredge to go into production. As part of this, it is important to work out the best type of recovery system to use, and decide how many production-shifts you will run. Night operations require special lighting equipment.

2) Doing enough samples along a stretch of river to prove that high-grade deposits are extensive enough there to justify bringing in multiple production dredges, and setting up a substantial support infrastructure.

3) Doing a series of controlled samples, an equal distance apart, along a portion of a river, to statistically-quantify the value of a mineral deposit. This is often done under the watchful eye of a consulting geologist who will certify the results in preparation for a larger-scale mining operation with the use of mechanized machinery that might float on platforms.

  

 

4) Doing a series of controlled samples, an equal distance apart, for some distance across an entire section of river, to quantify the average-value of the river gravels. This almost certainly would be accomplished under the guidance of a consulting geologist(s) who will certify the results, in preparation of financial instruments for investment bankers or a public trading company.

 

By Dave McCracken

This system combines two classification screens to more-effectively separate material-feed into three separate size-fractions, each which is directed into a different recovery system.

Dave Mack


Riffles in box Three sections of screen

Classification is the Key to Fine Gold Recovery

It is well-established that if you want to effectively recover finer particles of gold, you must first separate them from the larger-sized materials which are being washed through your recovery system by a higher-velocity flow of water. The small-sized material can then be directed to a milder-flow of water over a shorter set of riffles. The smaller you can classify the size of the material, which can be directed by and even milder flow of water over lower-profile riffles, the finer-sized gold that you can effectively recover.

This is all rather easy to accomplish with surface processing plants where earth-moving equipment can be used to feed a plant some distance above the ground. Feeding a plant well above the ground allows plenty of drop for water and gravity to direct material through multiple sizes of classification screens. Then, gravity can be used to direct the different size-factions of material to separate recovery systems with controlled water-flows and riffle sizes specifically designed to recover gold effectively from each size-fraction.

Conventional Suction Dredges do not allow for Much Classification

I am not sure what the exact formula is, but I know from long experience that every inch you lift the feed of a suction dredge above the surface of the water, you lose a considerable amount of suction-power at the dredge nozzle. Therefore, since we have to accomplish both classification and gold recovery from a feed that can only be effectively lifted about 4-to-6 inches above the surface, our options are pretty limited.

Dredge manufacturers have worked out different ways to direct classified materials into slower-moving recovery systems. Generally these methods fall into three categories:

1) Placing a classification screen over top of a set of riffles. This way, smaller-sized material can fall through the screen into a slower-moving flow of water over riffles that are more-protected from higher-velocity water-flow. You see screened-over riffles in common use today.

2) Placing a classification screen towards the head of the sluice box, and then directing the classified material to one or two completely separate sluices which have a slower-moving flow of water over lower-profile riffles. This was most commonly seen in the form of side-by-side triple sluices during the 80’s and early 90’s. While effective, the problem with the side-by-side sluices is that the side sluice(s) normally have to be placed on top of the dredge’s pontoons. Therefore, in order for gravity to make everything work right, the initial feed to the dredge has to be lifted higher out of the water. This causes a power-loss at the nozzle. So you do not see as many side-by-side recovery systems in production on suction dredges these days.

3) Placing a classification screen somewhere towards the upper-end of the recovery system, and directing the classified material to a slower-moving recovery system which is located directly below the main box. This is commonly referred to as an “over-under recovery system, and remains in popular use today. An over-under system is most commonly accomplished in the same basic sluice box, which is constructed with a removable false bottom. By this, I mean two separate recovery systems, one sitting over top of the other, in the same sluice box.

I cannot go into which of these systems are better or worse; because there are too many variables in play, and experienced prospectors can work it out to get the best recovery possible out of any of these designs, each which would likely be comparable to the other. That’s because all three of these system concepts depend upon a single classification screen to remove some portion of the smaller-sized material from the higher-velocity water-flow which is required in a dredge.

This particular discussion has more to do with the effectiveness and size of material-classification. Remember, with conventional suction dredges, we are using water-flow to move all our material across any classification screen(s) that we are using. The larger the dredge, the faster and more powerful the water-flow must be to wash larger-sized rocks and a larger volume of material through the sluice. The faster the flow, the less time that smaller-sized material has to drop through a classification screen. The smaller the openings in the screen, the less opportunity smaller-sized material has to drop through the screen. The shorter the screen, the less opportunity smaller-sized material has to drop through the screen.

Each of these factors combine into to the effectiveness of the dredge’s classification. For example, the substantial flow of water to move 5-inch sized material over 10 inches of 1/8th inch punch plate does not present much opportunity for minus-1/8th material to drop through the screen. So while a separate slower-moving recovery system might be doing a better job recovering smaller-sized gold, perhaps the classification system is only allowing 5% of the finer-sized gold to be directed into the slower-moving recovery system. In other words, the effectiveness of your recovery system is largely affected by how you are attempting to classify and separate the smaller-sized material.

Therefore, on the subject of fine gold recovery with suction dredges, our first challenge is to try and accomplish effective classification as best we can out of a strong flow of water (strong enough to move the largest rocks you are sucking up through the recovery system).

Years ago, we overcame this whole challenge on commercial dredges by working out a mechanized shaker screen at water level which provided 100% classification of the dredge feed. Minus-sized material from the screen was dropped into a sump where it was redirected by a gravel pump to an elevated feed on a surface-type recovery system either on the shore, or on a separate floating platform.

But it is impractical and too expensive to try and place a mechanized classification screen on smaller-sized dredges — which also must remain more portable for sampling. Therefore, on conventional dredges, until someone comes up with something different (if ever), we must continue to make due with a water-flow to wash material across our classification screen(s). With this in mind, here are a few principles which I believe to be true:

1) The faster the flow, the more difficult it is to drop finer-sized material through the openings of a screen in your sluice box.

2) The smaller the holes in the screen, the less finer-sized material you can expect to drop through the openings out of the high-velocity flow required to move larger material through your sluice box. Example: Using the same flow of water and material, you could expect more fine-size material to drop through a 3/8-mesh screen, than a 1/8-mesh screen. This is because the larger openings provide a bigger doorway for material to drop through.

3) The shorter the length of a classification screen, the less fine-sized material you can expect to drop though. Therefore, we want the classification screens to be as long as we can get away with. Longer screen means more opportunity for finder-sized material to drop through.

4) Effective classification of finer-sized material can be accomplished better in stages. For example, first drop 3/8-minus material out of the fastest flow in the box. Then, using a slower flow of water, direct the minus-3/8 material over a 1/8-inch screen.

5) Since we only have 4 or 5 inches of drop to work with from the feed of a conventional suction dredge, there is only room for two levels of classification screen before we must drop the finest-sized material into a recovery system. Otherwise, we will be underwater where reduced gravity is not going to allow water-flow to work for us, anymore.

What to use for a fine-gold recovery system?

material in rifflesAs I have explained elsewhere, I believe it is necessary to direct finer-sized material over lower-profile riffles that will continue to remain fluid under a mild flow of water, even when they are full of concentrated (heavy) material. If you have not reviewed the theory on this, I strongly suggest you read “The Size of Riffles.”

There are different kinds of low-profile fine gold recovery systems on the market. Just take a look around and make your own choice.

We have been using the green, plastic Le Trap sluices to reduce the volume of our dredge and high-banking concentrates all the way back to the early 90’s. I cannot overstate how effective these Le Trap Sluices are. When set up with the proper water-flow, a Le Trap will recover all the visible gold from a feed of minus-1/8th material with losses that are so minimal as to be meaningless. We know this from panning the tailings hundreds of times over the many years.

So when we needed something to recover overwhelming amounts of fine gold using a dredge on a river in Cambodia, I started giving a lot of thought to how we could more-effectively classify dredged material down to minus-1/8th, and direct the material in a controlled flow over Le Trap-type riffles.

Dredge 1Dredge 2

Several very experienced dredge-builders and I created the prototype several years ago from a Precision 6-inch dredge. To accomplish our objective, we assembled two layers of classification screen, each which could be independently raised or lowered, so that we could adjust the water-flow over the riffles, and over each of the screens. The top screen is 3/8-inch mesh. This is to allow the larger-sized material and strong water-flow to wash through the box without affecting the plastic riffles along the bottom. Minus-3/8ths material drops through the top screen onto a 1/8th-inch mesh screen, where the water flow is substantially reduced. Slower water-flow then allows finer-sized material more-extended contact with the 1/8th-inch screen.Double screens over riffles

Material that drops through the 1/8-inch screen is then carried over the Le-Trap sluice by a mild flow of water. By adjusting the height of the lower screen over the plastic riffles, and the slope of the sluice box, we are able to control the amount of water-flow over the lower-profile riffles.

Since the sluice box in the 6-inch Precision was much wider than a normal Le Trap sluice, the prototype required quite a lot of work in a cut and paste project (using of 4 or 5 Le Traps) to create the first underlay recovery system for a dredge.

Fine goldWe invested quite a lot of time and energy into the prototype. All you have to do is look at how much (very fine) gold we found on that river in Cambodia to understand why we did it. We were shipping this 6-incher over to resume (sampling) where we had left off on that earlier project.

 

During trials on the Klamath, I was amazed at how much (very) fine gold we recovered out of just a minute or so of dredging loose material off the surface!

Our trial run on the Klamath River near Happy Camp in March several years ago turned up so much fine gold out of the lose surface gravel, that I hesitated over sending the 6-inch prototype to Cambodia!

I have been told for 30 years that there is so much fine gold in the river that we are losing out of our conventional dredges, if we could just recover it, we could make the river pay just by pumping any gravel! This new system seemed to prove that theory may be true, especially with these higher gold prices. But it was March and the Klamath was cold; so we shipped the original prototype dredge to Cambodia.Cambodia Dredging

I devoted plenty of time in Cambodia (underwater) observing three separate flows of material coming off the back-end of the recovery system; and it was poetry in motion!

I have a non-disclosure agreement with our clients in Cambodia, so I cannot go into details or images of how well the new system performed over there. But I can say that I devoted a lot of time underwater watching water and material exit the sluice box in three separate flows; and the double-screen system is by far the best thing I have seen on a conventional dredge for effectively classifying material into three separate size-fractions.

Because of that, my experienced buddies and I invested quite a lot of time during the 2009 mining season to adapt the double-screen system to my 8-inch dredge. 8-inch dredge

Building double classification screens, so they can be adjusted up and down to allow you to set three separate water-flows through the sluice box, requires quite a lot of labor! But getting this right is the foundation of this whole concept.

Here are some video links which demonstrate the system being used on my 8-incher. These give you a much better look at how we created a double-screen classification system over top of the fine gold recovery: Take a look at the size of the gold we were recovering!

 

As (bad) luck would have it, the State of California imposed a temporary ban on suction dredging just as we completed the double-screen refit on my 8-inch dredge. This forced us up onto the Rogue River in Southern Oregon, where we are limited to smaller-sized dredges. So my 8-incher had to be set aside.

Picking up on the idea of my double-sluice conversion over a plastic sluice, one industry-fabricator was recently promoting the idea of refitting conventional sluices (using the plastic sluice underlay) which do not include the double-screen classification, and do not allow the screens to be adjusted. I would advise caution on short-cutting these concepts. That is what prompted me to write this article. Since these conversions must be accomplished through custom shop work, I wanted to provide you with some background so you can make your own decisions.

While there is still a lot to learn, for the reasons I outlined above in points 1 through 5, I personally do not believe that you can classify raw material effectively from a 4, 5 or 6-inch (or larger) dredge being washed across an 8-mesh screen by high-velocity water.

I believe effective classification must be accomplished in stages; first to drop the 3/8-minus material out of the higher-velocity flow which is needed to push the larger-sized material through the sluice. Then, drop the 1/8-minus out of the much slower flow necessary to wash 3/8-inch material across the lower screen.

I believe you have to be able to adjust the height of each screen (set the water velocity) in order to get a workable water-flow over the riffles and over the 1/8-mesh screen. The water-flow cannot be so much that you boil-out the riffles, and it cannot be so little that you load the riffles. You also must not pack up the space between the two screens!

Eric Bosch and I first experimented with this double-screen concept in the early 90’s. But we made the mistake of fixing both screens (welded them where we estimated they ought to be). Our estimate of how much water-flow was needed between the screens was incorrect; the space between the screens packed solid with material; and the whole system failed.

Also, if you cannot adjust the water-flow over the riffles, and between the screens, you cannot compensate for different conditions in different areas.

Dave's goldAs an example, there is an overwhelming amount of heavy black sand and small iron rocks (and lead) along the Rogue River in Southern Oregon. We do not encounter this magnitude of heavies on our properties along the Klamath River in northern California. The heavies along the Rogue completely overwhelmed my fixed recovery system (buried the riffles on my 5-inch conventional dredge) at the beginning of last season. This prompted me to place smaller riffles below my (fixed) screen, spaced further apart. That worked better, and I recovered a lot of gold. But I believe I lost most of the (very) fine gold (I could see it in the last riffle) that was fed into my sluice box. This has prompted me to refit the recovery system on one of my 5-inch dredges for the upcoming season.

The images at the beginning of this article show an early version of the double-screen system that was designed for deposits we located in Cambodia. We did not find a single particle of gold on that river that was larger than the size of a pinhead. Since larger-sized gold was not present, we did not want to waste the (very) limited amount of room we had to work with by installing riffles for larger gold. Those images are helpful in showing the plastic sluice underlays (there are two of them, one following the other).

The images at the beginning of this article show the Cambodian version of the double-screen refit. Those images are helpful in showing the initial plastic sluice underlays that we were using (there are two of them, one following the other).

Header areaHeader with screen and miners moss

The images in this article also show a header section near the upper-end of the box. My initial theory was that the initial impact of the water and material must bottom-out on something other than plastic sluice underlays. We experimented with a combination of different kinds of heavy screens over top of miners moss or ribbed rubber matting to absorb the initial force of the water and material where it bottoms-out at the head of the sluice box. Fortunately, nearly everything we have tried in the header section seemed to work really well. As you will read below, we have since evolved completely away from using plastic sluice underlays… Header area after running

This is what the header area looked like under the screens when we shut the dredge off while dredging at production speed. You can see how classified material kind of mounds up there before flowing onto the slick plate of the riffle system. We are finding that quite a lot of (very) fine gold also gets trapped in the header section!

We have noticed that while in production, material tends to mound on top of the header section under the 8-mesh screen, and then wash off the mound onto the first sluice underlay. This is really good, as long as the mound does not rise up and pack-up the whole space between the screens.

While we were still using them, the plastic sluice underlays followed just behind the header section. This allowed water-flow and material to settle out and slow down before being washed across the lower profile riffles.

 

 

 

Two kinds of rifflesriffle section

Notice that the shorter section of riffles (remains protected by the top screen) are present only to process classified material which washes across the 8-mesh (lower) screen in the box.

Adding larger riffles for bigger gold

We have since evolved the system, adding two sets of different-sized riffles to catch larger-sized gold. We accomplished this by replacing one of the 1/8-mesh (lower) screens with a solid bottom that supports both sets of the added riffles. The false bottom continues to allow an under current to wash minus 1/8th material across a low-profile underlay, just like in the Cambodia version.

The first set of riffles on top of the false bottom is designed to process the material that drops through the 3/8-inch screen, but is too large to drop through the 1/8th-inch screen (1/8th-to-3/8th size-fraction). This would be for small nugget-sized gold. That size-range of gold is very easy to recover.

As I discussed in The Size of Riffles, the height of a riffle necessary to recover a piece of gold normally does not need to be much taller than the size of the gold you are trying to trap. So the first set of riffles for larger gold can be rather short. Notice that the first set of riffles continues to be protected by an extension of the top screen.

Then we added a final set of open riffles (not covered by a classification screen) to catch any gold we might suck up that is larger than 3/8th-inch (larger nuggets). For example, depending upon where you dredge, the Rogue River in Southern Oregon can produce a lot of gold in these larger sizes. But the river is loaded with fine gold, as well.

It is kind of hard to see in the images; but if you look close, you can see the plastic sluice under the false bottom where we placed the riffles for larger gold.

Since you cannot buy these double-screen systems ready-made, you either have to refit your own sluice, or arrange with a capable fabricator to do it for you. With this in mind, I will follow with some basic directions which we have learned from building several of these systems:

Building the System

If you look at a Le Trap, you will see that it has 3 important sections: There is a slick plate at the top. This is vital; because it allows the water-flow to smooth out before material encounters the riffles. Then there are some short riffles. These capture all the gold unless you over-feed the box with too much material at once, or unless you completely fill the short riffles with gold. Then there are some deeper riffles which more-aggressively capture all the rest of the gold when you do over-feed the short riffles up front. “Overfeeding” has more to do with the amount of heavy iron material, than light sand or gravel. I will talk more about this down below.

Close-up of rifflesThis image shows two sluice underlays following the header section (with no screens on top)

When we planned these sluice underlay riffle-panels, we included the slick plate up front, and then went about 50/50 the rest of the way using short and deep riffles. We did this because I wanted more of the short-type riffles that work so well in the Le Trap. But I did not want to eliminate the deeper riffles which create such a strong back-flow, especially at times when lots of material is being fed across the box. But through extensive trial and error using the third evolution of this system this past season, we discovered that the higher velocity flows that are necessary to move volume-amounts of classified material across the plastic riffles were also causing some of the trapped fine gold to boil out of the system. Too bad! We then tried Keene’s new ribbed rubber matting (good stuff!) and ended up with the same result (we were losing some gold). So it appears that these plastic and rubber riffle systems are better suited for final concentrating work, rather than being used in the volume production setting inside of a dredge recovery system (more on this below).

Because the double-screen assemblies are heavy, in order to manage them, you have to divide your sluice box into several smaller sections. How many sections depends upon how long your sluice box is. You will notice in the images at the top of this article that we divided my 5-inch dredge into three separate sections. One section is over the header area. The other two sections are over top of two identical sluice underlays. It is wise to divide the sluice underlay sections into exactly the same sizes. This way, the parts can be interchanged when it is time to reassemble your recovery system.

We build the double-screen assemblies so they rest exactly upon the sluice underlays. This allows us to take apart one only portion of the sluice box if that is all we want to look at or clean-up.

The screen assemblies are built so the aluminum side supports slide down inside the sluice box and sit directly on top of the side rails of the sluice underlays. This pins everything down snuggly against the bottom of the sluice box. Then we snap the screen assemblies down tight to make sure everything stays in place when we are running the dredge or moving it around on land or in the river.

Sluice Underlays

Close-up of matting
Close-up of both

Through a very substantial amount of trial and error this past season, we discovered that both the plastic sluice material and also the new Keene rubber matting were losing gold from under the twin screens.

Expanded metalWe finally found the right combination by using a wide, raised expanded metal over top of deep ribbed rubber matting. The aggressive expanded metal was dropping the gold out of the classified feed. Once it was in the ribbed mat, the gold was not getting away. This combination was so effective, we even replaced our header section with the same expanded metal, though we used miners moss underneath, rather than ribbed rubber matting.

We did multiple checks; and we were never able to find a single speck of gold in the final 25% of our recovery system, even though we were mostly dredging in fine gold pay-streaks (loaded with fines in the front section of the recovery system) all season.

This is important: The width of the sluice underlays (and screen assemblies) have to be a bit narrower than the inside of your sluice box. Otherwise, it is too difficult to get them in and out when you want to perform a clean-up or reassemble the recovery system. I always allow a margin of around 1/8th or 3/16ths of an inch, maybe even ¼-inch on a wider sluice.

Note: We have since replaced the sluice underlay in the drawing above by welding some 3/4-inch angle iron on both sides of the expanded metal to create side rails that the double-screen assemblies can rest on top of.

The following video sequence should give you a better idea of what we have ended up with as a sluice underlay:

The width of your side rails needs to be greater than the margin you are allowing between the sluice underlay and the side of your sluice box. This is so you will be sure that the sides of the screen assembly are going to slide down and meet the rails of the sluice underlay.

Double-screen Assemblies

Sliding the second screen into the frameThese add up to some weight; so you have to plan how to divide your sluice box into small-enough sections that you can lift the screen assemblies out of your sluice box without too much trouble. On the other hand, you want to minimize how many sections you have to make, because these are very labor-intensive to build.

The length and width of the screen assembly should match the sluice underlay, so that they will marry-up exactly when you set the screen assembly down on top of the underlay.

 

Screen LatchYou have to use aluminum plate for the sides to keep the overall weight of the screen assembly from adding up too much. The height of the sides needs to be at least as tall as your sluice box. I build mine high enough that I have room to adapt a latch to snap everything down tight.

Once you have the aluminum sides of your screen assembly cut to size, bring them all to your local machinist, and ask him to mill slots so that you will be able to raise and lower your two screens. If you bring the machinist one of the lag bolts you are going to use, he can mill the slots just wide enough to allow the lags to slide up and down freely, but not so wide that the lag is allowed to turn in the slot when you are tightening or loosening the nuts that hold the screens in place. Just to make sure I will have the full range of adjustment, I have the slots milled nearly the full height of the sides, to within about ¾ inch of the edge, equally at the top and the bottom. Each aluminum side needs three slots; one on each end and another in the exact middle.

You can source thin-headed lag bolts from fastener supply outlets. If you look, I’ll bet you can find them on line. If you cannot find them, then you have to grind the heads down on regular lag bolts, because normal heads are too thick and will take up too much space between the screens and the sluice box.

Helpful hint: The head-thickness of lag bolts on both sides of the screen assembly need to be included when you are deciding how wide your screen assembly and sluice underlay need to be for everything to slide in and out of your sluice box without too much difficulty.

Another helpful hint: If you cut the side plates all the same size, and have the machinist mill the slots exactly the same on all the plates, all the pieces will be interchangeable, and then you can jig-up to drill standardized holes in the side rails to your classification screens.

The lag bolts need to be heavy enough to support the weight of your screens (perhaps 5/16ths or 3/8ths). Different boxes have different widths, meaning heavier screens. It is better to go a little heavy on the lag bolts. The bolts need to be long enough to extend through the aluminum side, through the side rail of the screen, and have enough room for a flat washer and self-locking nut.

Screen frameStacking screens

Ideally, you build all your screens exactly the same size, so they can be interchanged. We accomplish this by rigging up a jig to cut all the side rails exactly the same; then to weld the frames all the same; and then to drill all the bolt holes the same. We drill the bolt holes in the side rails a little large to allow some margin for error.

Side rails for the screens need to be heavy enough to support the weight of your screens with you standing on top of them. By heavy, I am discussing rail thickness. Because, if you go too wide, you will limit how close you can adjust the distance between the screens. Thicker 1.25-inch-wide strap has worked well on my refits for the screen side rails.

Unless you want to buy whole new sheets of screen (expensive), I suggest you source used screen at your local metal scrap yard. The one we go to in White City, Oregon nearly always has a large supply in all mesh sizes. I gather that commercial screening plants replace their screens pretty often – most of it still in good enough condition to meet our needs.

The top screen (around 3/8th-inch openings) needs to be heavy enough to span the length and width of your screen assemblies without needing additional support, and without bending or sagging when you stand on top of the finished screen.

The lower screen (around 1/8th-inch openings) needs to be heavy enough to span the length and width of your screen assemblies without needing additional support.

Helpful note: I experimented with a finer-mesh lower screen (about 1/10th-inch openings), and had trouble with small particles of rock plugging up all the holes. We call this “blinding.” It’s when the holes in a screen all become plugged-up (or overwhelmed by too much feed), preventing the screen from doing its job. So it would appear that you do not want to use a mesh on the lower screen much smaller than 1/8th-inch.

Cutting screenWe have had good luck cutting the screens to size using a cutoff wheel on a hand-held grinder. If your side rails are made of thick material, you should be able to cut the screen to size and weld it down directly on top of the side rail frame. Grind all the edges nice and smooth, so your hands are not getting cut up once you start working with these screens on your dredge.

Helpful note: If you weld the bottom screen on top of the side rails, and the top screen on the bottom of the side rails, you will be able to loosen or tighten the center bolts in the side plate much more easily. I am talking about the lag bolts which attach the screens to the aluminum side plates. If you end up with your center bolts between the screens, it is much more difficult to get at them!

Another helpful note: You might want to drill your holes just off center through the side rails. This way, you can still get a socket on the nuts after the screen is welded on.

These helpful notes are things I have learned the hard way!

When you assemble the screens, a good starting point would be so that the bottom screen rests maybe just a little more than an inch above the plastic sluice.

Helpful hint: If you make the side rails on your sluice underlay too tall, it will limit how far down you can slide your lower screen.

We have had pretty good results lifting the upper screen about 1.25 inches above the lower screen.

This is important: To add more flexibility, if not already present, we modify the sluice box supports on the dredge so that we can raise and lower the slope of the box. This creates a very helpful mechanism for adjusting flow rates.

Once in the field, you can make adjustments to sluice slope and height of each screen to work out the needed velocity in three separate water-flows: First, the water-flow across the sluice; then the water-flow between the screens; and finally, the water flow across the top screen.

I already discussed above how to replace the lower screen with a false flat bottom which you can place riffles on top of to recover the larger classifications of gold. In my view, it is more effective to do this in the lower section of the sluice box (though, I mounted the riffles for larger gold in the upper-end of the sluice on my 8-inch dredge). I know this viewpoint is not popular with some prospectors, because they do not want to chance losing a bigger piece of gold that is allowed to get so close to the end of the recovery system. My answer to this is that gold is really heavy stuff! If there is some anomaly (like the gold is attached to quartz rock which makes the piece lighter) that would keep it from trapping in a set of riffles in the back-end of the box, it probably will not drop out in the front portion of the box, either.

Other than in a very rare occasion, the vast majority of the gold you will recover is small enough to drop through an 8-mesh screen. Some important part of that gold is so fine as to be difficult to recover using the recovery system on a conventional suction dredge. The journey of fine gold through 20 feet of suction hose, and then up through a diffuser (flare jet) places most of this fine gold right on the bottom of the material as it first flows into the sluice – right where you want it; right where it is most likely to drop through the classification screens out of the higher-velocity flows, which otherwise can wash it through your box like sand. Better, I think, to get the minus-1/8th gold into a safe holding area as the first priority.

If you look closely at the diagram just above, you will see another reason to put the larger riffles towards the rear-end of a double-screen system. See how all or most of the fines are directed through an undercurrent below the larger riffles? This means the larger riffles will not be getting flooded and loaded up with fine-sized material. So, while fine material gets more exposure to low-profile riffles (where it belongs), the deeper riffles remain more open so that larger gold has a place to drop out of the flow.

But that is just my view. You guys can do it any way you decide to!Riffles just after shut-down

The reason you see rocks on top of the double-screens, is because we turned the dredge off while we were pumping at production speed. See how the riffles are working? They are not loading up, and they are not boiling- out. This means the system was working!

I do my classification and sluice flow adjustments when running the dredge at normal operating speed while I am feeding the nozzle at production speed in hard-packed streambed. I arrange for a second person to kill the motor without notice. Then, when I disassemble the system, I can see how the sluice and screens are performing while I am pumping gold and gravel into them at production speed.

Between these explanations, the drawings above, the images and the video segments, you guys (or the fabricator who will help you) should be able to see how these systems come together, and how they work. They provide you with a whole lot more than I started with!

Here follows a video segment we put together at the end of this last season which demonstrates the most recent evolution of this very effective dredge recovery system:

Other Considerations

Trial runPossible need for added floatation: As I mentioned above, these double-screen assemblies are heavy. So if you do a refit of your sluice, you may also consider adding some floatation to your dredge. When I refit the original 6-inch Precision dredge for Cambodia (image above), I also had new, larger aluminum pontoons made up to provide enough floatation so that I could also stand on the dredge while it was running. Nice!

Having enough water-flow to make double-screens work: Every dredge is a bit different. Before refitting your dredge with a double-screen system, you might turn the dredge up and watch the water-flow across your existing recovery system and estimate if you will have enough water volume to provide sufficient velocity to meet the needs of three separate flows.

Overfeeding the system: Every recovery system has its volume-limits! Since I find nearly all of my high-grade gold associated with hard-pack, I design my recovery systems to process average material which makes up normal hard-packed streambed that was put in place during the evolution of a major storm event. Normal streambed consists of rocks which are fitted together, with smaller rocks and pebbles in-between, with gravel, sand and silt filling the smaller spaces. When taking apart normal hard-packed streambeds, the smaller-sized material only comprises a small fraction of the overall volume. Therefore, I have yet to overwhelm one of these double-screen systems while production-dredging in hard-packed material.

On the other hand, if you go out on the river and just start pumping sand or loose, classified gravel (like tailings), a much-higher percentage of the material will penetrate the screens and you will almost certainly overload (blind) the sluice with too much material – and perhaps even pack-up the space between the sluice and the bottom screen. Let me be clear: This double-screen system is not designed to process sand or loose gravel deposits or tailings from some earlier mining activity!

This same concern is true for any type of recovery system used on a suction dredge. So it is important for you to be mindful of the material that you are feeding into your suction nozzle. If it is a layer of sand or loose gravel, you should either slow down; or you can speed up and pump it through as fast as you can; and then go up and make sure your system is no longer packed-up before you start feeding pay-dirt into your dredge.

The fine gold needs to be present: The only good place to test the effectiveness of your recovery system is when you are feeding high-grade into your dredge. The more gold you feed into the recovery system, the better you can see how well it is working.

Effectiveness cannot be discounted just because you see a speck or two of gold down towards the end of your box. The thing to look at is where most of the gold is stopping.

So many times, I have watched others decide their recovery system is not working, only because they are not recovering much gold. You cannot recover much gold if it is not present in the streambed that you are dredging! So I suggest you reserve judgment until you test your system in high-grade.

 

 

BY MARCIE STUMPF/FOLEY

There is a fairly new method of mining out there in the mining community that is rapidly gaining in popularity, with good reason. It is called “Vacking;” and, as you might suppose, involves vacuuming material.

As a suction dredge vacuums material from the bottom of the river, this is a type of dry-land dredging. It involves using a small, lightweight unit to vacuum cracks and crevices of exposed bedrock, moss on exposed bedrock or boulders, or material in a dry wash in the desert. For this “dry land dredging,” however, there are no uncomfortable and expensive wet-suits to don, no heavy equipment to carry and then set up, and no long period of learning how to operate the equipment, or learning where to find gold.

Anyone who is familiar with mining knows that there is a much larger proportion of fine gold deposited than large gold, in almost any area. Each winter, as the rivers swell with winter rains and snows, much fine gold is washed down them. The fine gold, since it is much lighter in weight, is deposited much higher on the banks, or in the material of the river. As the high waters recede with the onset of spring and summer, much of the areas where the fine gold is deposited is left exposed up on the banks of the rivers.

The new units consist of a two-cycle gasoline engine mounted on a five gallon container, which is equipped with a suction hose and a crevice nozzle. They are very efficient at pulling the fine gold from moss, and at cleaning out crevices. Previous efforts to accomplish this by hand were slow and painstaking, and not very efficient. Collecting fine gold has always been one of the greatest challenges facing any miner, and some people spend years attempting to perfect their fine gold recovery.

Not only does “vacking” do an excellent job at recovering fine gold — it is a lot of fun! It is so fast, simple, and easy to use, that it seems to take all the work out of mining. You are still out in the great outdoors, still getting healthy exercise, but all that’s left when you remove the excess work is the fun.

Since we live and work very near a gold-bearing river, if my husband can squeeze two hours of time, he can get to his favorite spot, set up, get in most of that time mining; and still come home with enough gold to feel he has been mining. If he is dredging, that’s not enough time to more than set up and get started before he has to quit!

These units come on their own back-pack frame, and all accessories are carried right inside the unit. It is a completely self-contained unit, and includes an extra fuel bottle, a crevice tool, a gold pan, a “sniffer bottle” to remove the gold from the pan, and even a sample vial to keep it in. With all these accessories, the unit weighs just 15 lbs., so you could hike into the back country with it without undue strain.

Many wives who are not interested in dredging or motorized sluicing (high-banking) enjoy using this type of unit because it is something they can do completely on their own. The only problem we have seen develop is that when some of the husbands see that the gold recovery exceeds that of their dredge or motorized sluice, they want to use one also. Then, they either fight over the one unit, or join the growing group of “two-vack” families. Since they are such low-cost units, this is pretty easy to do.

I recently talked to one avid vack-miner who has been using one of these units for two years. He was concerned that he might possibly lose some of the fine gold out the exhaust as the unit filled, since it is so lightweight. Shortly after purchasing his unit, he fitted an elbow and extension over the exhaust, and directed it into a container of water. He has used it faithfully, and panned out the light powder that accumulated each time. He has never found even a speck of gold in it.

A crack or crevice in exposed bedrock that runs crossways to the current of the river acts as a natural riffle, catching fine gold just as the riffles of a sluice do. The moss that accumulates on exposed bedrock acts much as the carpet in a sluice, only better! It is amazing just how much fine gold can accumulate there. These are prime areas for vacking.

Areas where people have been working with motorized sluicing equipment have also proven to be good. Even if they have worked the area down to the bedrock, they have been unable to clean the area as thoroughly as it can be cleaned with a Vack, and generally, the richest areas are right on the bedrock.

The greatest demonstration I have ever seen about how gold traps in bedrock and moss, and how much work it is to recover it using conventional methods, is contained in Dave McCracken’s video, “Modern Gold Mining Techniquies.”

Although I have not mentioned finding nuggets with this equipment, it certainly does find them! Even areas that have predominantly fine gold in the high bedrock will trap nuggets during flood storms, and if they are there, this equipment will help you get to them as nothing else will.

Since you do not work directly in the active waterway, and this equipment does not put anything into the waterway, there are no dredge permits required for the use of these units, at least in the state of California.

All in all, Vacking has such a wide range of applications, in so many areas of the country, by such a wide range of people, that the gain in popularity is very understandable. It can only be expected to grow.

If you should get the Vacking bug, be sure you look for us out there, because that’s where we will be every chance we get!

 

BY SAM LONG

 

Dry-washing, in many ways, puts me in mind of eating at a Chinese restaurant with chopsticks. It’s fun to try; but you can’t move material from one place to another very fast, even if you’re good at it. That’s why it’s so important to pick out an area with a theoretically high concentration of gold. Of course, down here in Arizona, you’ve got about as much chance of finding an area like that as a one legged man’s got at winning a kicking contest!

That’s not to say you shouldn’t try. I always do so with this theory in mind: Billions of years ago, when God was putting tons of gold in Alaska, South America, Russia, Australia, the Yukon, and even California, he accidentally spilled a couple of pounds over Arizona. I always think of that after I’ve worked through a pile of rocks and sand big enough to shade an elephant, and not come up with enough gold to fill a tooth. All the expert mining techniques in the world won’t come up with a speck of gold where there’s none to begin with. So, the place to start is history.

I know you’ve read it a thousand times. Now you can say you’ve read it over a thousand times: It’s usually better to begin your search for gold in an area that has produced it in the past. The more the better.

From that point, go to maps. Study them religiously. I take my topographical maps to an office supply that has an enlarging copier. I have the section I’m interested in blown up two or three times. This really helps in seeing all the side washes, forks, bends, and places of slowing water that are the obvious holding spots for gold.

Now, you’re ready to hike to these areas. Of course, on your way to and from these spots, keep your eye open for any likely looking area you might have overlooked on your map. There are a zillion of them, so you’ve got to learn to be very selective.

Remember, you want to shovel rocks, sand, and gold through your dry-washer, not just rocks and sand. It doesn’t matter to your shovel. It doesn’t matter to your neighbor. It only matters to you. Take your best shot before you ever crank up your machine, and you won’t have to deal with the disappointment of getting skunked.

And, just how do you do this? Sampling. That’s right— sample, sample, sample. If you’re diligent about it, and do it correctly, when you finally start dry-washing, your question won’t be will I find gold? It will be how much will I find?

Starting up your dry-washer in a likely-looking spot without sampling, makes about as much sense as a dog barking at a knothole. Sure, sampling is a lot of extra work and it takes time. But, when it’s all said and done, you’ll end up with some gold along with the new blisters–instead of a sour attitude and the new blisters.

This isn’t to say you can’t set up anywhere and get some color. But to my way of thinking, that would be pure luck; and I haven’t experienced enough of that to feel qualified to write about it. If you have, and can make it work time and time again, I’d sure be willing to learn.

So, here we are in a gold producing area, walking up a wash that had some likely-looking gold-holding spots on our map. How do we sample? Well, as with most things, there is more than one way to skin a cat. I use a Goldspear. It’s proven itself to me to be an accurate, time saving, prospecting tool. I know lots of folks don’t think much of them, but usually they haven’t ever owned one, or don’t understand how to use them to their advantage. Granted, they’re not some super tool that can automatically find gold. But used correctly, they can sure save you a lot of needless digging. And, at the price of shovels these days, you don’t want to wear out any more than necessary.

For now though, I’ll skip the use of the spear and explain a few points of how I sample without one. Again, this isn’t the only way to sample or dry-wash, but it works for me. Adapt it to your own personality and tools, as you see fit. In my pack, my basic tools are: Two pans, a small kitchen sieve; and, because we’re prospecting dry washes, a wide-mouth plastic gallon jar of water. Needless to say, never go anywhere without your rock pick.

With these basic tools, slowly work your way up the wash, visually sampling as you go. In your mind’s eye, continually look for the places gold is likely to accumulate. The more of these types of places you can recognize, the more success you’ll have in sampling.

Likely gold-holding areas would be the inside of sharp bends; areas where the wash levels and widens, indicating slowing water; areas of red and blue clay; pockets of iron pebbles, which show the water’s inability to carry heavier minerals; or a zone of magnetite, hematite or quartz. All these are good visual indicators that gold will likely be present.

After finding a place containing as many positive indicators as possible, roll over the biggest boulder you can in that area; and using one pan to hold the water, screen some material from under the boulder into the other pan and go to work. If you’ve done your homework right, this should yield you a few colors. Jot down how many on your map at the place where you found them. If more than just a few colors materialize, try a couple more pans before moving on. Continue in this manner for the rest of the day. You should have a few different areas that are somewhat better than the others.

Now that you’ve picked a good spot to work, and packed in all your equipment, the last important point is the speed at which you run the material through your dry-washer. It’s a big temptation to drop your riffle board too low so you can process material faster. But by doing this, you’ll lose a lot of finer-sized gold. As you either know, or will soon find out, most gold in the dry washes is very small. Unless you keep your riffle board only slightly lower than level, a good portion of the fine gold won’t have time to settle. It will end up going over the end instead. You can’t feed any more material in than is going out, so be careful not to overfeed the hopper. Otherwise, you’ll end up with gold in your tailing pile. Nothing will make you feel ankle high to a frog in a post hole quicker than your neighbor coming by, to run his Goldspear through your tailing pile, and getting enough beeps to make a liar out of you, when you tell him you were planning to run it through again a second time anyway.

The biggest hindrances to running your machine are laziness and rain. If you’re the type who does more spitting on the handle than shoveling, you’ll probably welcome the rain. If not, the folks around you will surely think you were raised on sour milk. It takes the fun out of dry-washing when you just get going good, then it rains and stops your operation. That’s what happened to us this winter. With my Keene dry-washer, I could work wetter dirt than everyone else because it blows hot air. But after the fourth cloudburst, it was even too wet for me. We switched it to a re-circulating water system and kept going.

So, if you pick the right spot and don’t push your machine, you’ll get some good gold. It might not be the most gold you’ll ever get in a day, but that desert-gold is some of the prettiest you’ll ever find. Since gold is more ornamental than useful anyway, you ought to be happier than a fly in a raisin pie

 
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By Dave McCracken

Always set up a dry-washer downwind of where you are working!

Dave Mack

 

Deserts consist of huge deposits of sedimentary material which have been affected by ancient ocean tides, ancient rivers, glaciers, floods, gully washers and windstorms. They are literally a gold mine of placer deposits.

There is also an enormous amount of gold-bearing mountainous dry placer ground which has remained relatively untouched by large-scale gold mining activity because of the scarcity of water required in those locations to support wet recovery methods.

Generally speaking, dry methods of gold recovery are not as effective or as fast as wet recovery methods. Yet, dry methods do work well enough that they can produce gold well if the ground is rich enough. Recent developments in dry washing equipment have made it possible for a one or two-man operation to work larger volumes of dry placer ground without water, and obtain good results in gold recovery.

Dry processing recovery systems generally use air flows to do the same job that water does in wet recovery systems. Under controlled conditions, air flows and mechanical motion and vibration can be made to effectively get rid of lighter, worthless materials. This causes a concentration of heavier materials similar to what occurs in wet processing.

SETTING UP TO WORK AN AREA

Sometimes a road can be bulldozed to your spot. Sometimes you can drive right in with a 2 or 4-wheel drive truck. In these situations, you might consider screening pay-dirt into the back of a truck and hauling it to a wash plant to be processed elsewhere. Actually, this is just slightly more difficult than shoveling directly into a wash plant. The hardest part is breaking the material away from the streambed and classifying it. It takes a little more time to haul the material to the wash plant, but that depends upon the distance and the condition of the road. It is also more difficult to shovel up into a truck. Some small operations use a portable conveyor belt to lift the material into their truck. Feeding the material from a truck into a wash plant is not as difficult, because it is usually down hill. An average one or two-person team should be able to move the equivalent of a pickup-sized load of screened pay-dirt and process it through a wash plant at another location in the period of a full day’s work-perhaps even two truckloads, depending upon the distances involved. If the material is paying well, they could do well at it, too.

DRY-WASHING PLANTS

If conditions do not allow you to truck the pay-dirt to a nearby water site to be processed by wet methods, you will have to consider processing the rich material by dry-production methods.

While dry-panning and winnowing do work, and have been broadly used as a means of production during the past, they are not normally as effective as some of the modern dry-washing plants which are available on today’s market.

Dry-washing machines use an air blowing fan or bellows-type device to blow a controlled amount of air-flow up through the dry material that is being processed. Air flows help blow off the lighter materials and allow the heaviest particles and gold to collect.

Dry-washing plants are available which can either be operated by hand or by lightweight engine and air-fan assemblies.

“Non-motorized dry-washing unit”

A hand-operated dry washing plant usually includes its own classification screen as part of the unit. Raw material can be shoveled directly onto it. The bellows air-blower is usually operated by turning a hand crank, which is often conveniently located so that one person can both shovel and alternately work the bellows at the same time. Under ideal conditions, two people working together can process up to a half-ton of gravel per hour by taking turns, one person shoveling while the other works the bellows.

Some units also have a 12-volt electric conversion kit to allow you the option to either hand-crank in the field or connect to a 12-volt battery for automatic bellows operation.

Various gasoline motor-driven dry concentrating units are available on the market which utilize static electricity and high-frequency vibration to help with gold recovery. Most commonly, there is a high-powered air-fan which pumps air through a discharge hose into the concentrator’s recovery system. The air currents which pass through the recovery system are adjustable so that the proper amount of flow of lighter materials through the recovery system can be obtained-similar to a sluice box in wet-processing. The purpose of the steady airflow is to “float off” the lighter materials through the box. Heavier materials like gold will have too much weight to be swept through the recovery system by the flow of air.

The bottom matting in this type of concentrator is usually made up of a specialized material which creates an electrostatic charge as high velocity air is passed through it from the air discharge hose. Fine pieces of gold, while not magnetic, do tend to be attracted to surfaces which have been electrostatically-charged, similar to the way iron particles are attracted to a magnet. So the bottom matting in these concentrators often attract fine particles gold to itself and tends to hold them there.

Some motorized dry concentrators also use a high-frequency vibrating device to keep the entire recovery system in continuous vibration while in operation. The way to get gold particles to settle quickly down through other lighter materials is to put the materials into a state of suspension. The vibrating device on this concentrator helps fine particles of gold work their way down through lighter materials that are being suspended by air-flows.

Here follows an excellent video demonstration which shows exactly how motorized dry concentrators work:

A motorized dry-washing machine is excellent for the production demands of a one or two-person operation. Under ideal conditions, it is able to process up to about a ton of raw material per hour, which is the equivalent of what a medium-sized wet sluicing operation can produce. This is as much or more than one or two people can usually shovel at production speed when working compacted streambed material. Most motorized dry-washers do their own screening of materials and almost everything else automatically. This leaves the operator free to produce at his or her own comfortable speed.

Total weight of the average motorized dry-washer is about 75 pounds, but the units do break down into separate pieces which can usually be carried around by a single person. So the electrostatic concentrator can be carried to a hot spot if it is worth a few trips to do so. They usually get about 3 hours to the gallon of gasoline.

SETTING UP A DRY-WASHER

There is no fixed formula for setting up the proper air flows and downward pitch on the recovery system of a dry-washer. A lot depends upon the nature of the material that you are processing, how heavy it is, whether or not the material is angular or water-worn and the purity (specific gravity) and size of the gold being recovered. Each of these variables is likely to affect how you must set your recovery system in each different place that it is operated.

The main thing to remember is that the machine needs to separate the gold from the lighter, valueless materials. If you only have a small amount of air-flow running through your dry-washer, then you will need more pitch on the recovery system-and you may need to feed the material slower. Too much air flow can also be a problem. Normally, you would compensate by adjusting to a lesser pitch on the riffle board.

Watch how the material flows over the riffle board. You should see the dirt rise up in an orderly fashion and flow over top of each riffle. It looks an awful lot like water. It is best to keep a steady feed of material going through a dry-washer at all times. The riffles should be filled about half to three-quarters, with a steady flow moving from one riffle to the next. The material in the riffles should have a fluid look to them; they should not be packed solid.

This following very important video sequence demonstrates how to set up and operate a motorized dry-washer, and it shows exactly what you should look for while making flow adjustments to obtain optimum gold recovery:

It is a good idea to shovel lower-grade material into your dry-washer while adjusting for the proper air flows and pitch. Once set, you can shovel in the pay-dirt.

One thing about dry-washing is that because it is generally slower than wet methods, the pay-dirt must have more gold. High-grade areas in the deserts certainly do exist! This is all the more reason to make sure your recovery system is set properly before processing pay-dirt. Chances are that you will not see any gold that might be discharged into the tailing pile through a dry-washer recovery system.

Another thing about setting up a dry-washing production program is that you always set up a dry-washer downwind of where you are working!

Once gold falls into the dead air space within the riffles, it will usually stay there. The air-flows are generally not strong enough to push gold out of there. There is a limit to this, however. Just like a water recovery system, a dry-washer will concentrate the heaviest materials which it processes. After some time, the heavier concentrates may require stronger air flows or a steeper pitch to keep them in suspension. At this point, it is probably time to clean up the recovery system and start all over again. If you are keeping a close eye on your recovery system, you can see when it is time to clean up. The fluidity of the material inside the riffles becomes more concentrated and slows down.

DRY-WASHING AND CLAY-LIKE MATERIALS

Material to be processed must be thoroughly dry to get the best results out of any dry-washing plant. Sometimes you will run into moist clays when out in the dry regions-just like you do in the wet streambed areas. It is also possible to find a pay-layer associated with the clay. Clays make dry-washing procedure more difficult, because they must be thoroughly dried out and broken up before being processed effectively by dry methods.

Sometimes this means the material needs to be set out in the sun to dry for a full day or more before anything further can be done with it. Sometimes it is necessary to dig clay a couple of days ahead of the processing stage. You can alternate spending a day digging and laying out material to dry, and then a day processing dried material. Sometimes, the dried clay can harden into clumps, which then must be broken down into dust and sand before you can recover the gold out of it. When necessary, all of these requirements require more time and energy. But if a good pay-streak is involved, you will find yourself doing whatever is necessary to recover the gold out of it.

It may be necessary to use rock-crushing machinery to break up hardened clay-like material and crush it down on any kind of a production -scale.

The clean-up of concentrates from a dry-washing plant is accomplished best by wet-processing methods. Usually, if you have room-enough to haul around a dry-washing plant in your vehicle, you will also have room for enough water to pan down your final concentrates, too. The following video sequence demonstrates how and when to perform a final clean-up during dry-washing:

If water is not available to you out in the field, the clean-up of your dry concentrates can sometimes be accomplished quite effectively by running them through your dry-washing plant several times. Final cleanup procedures can then be done to separate the gold from the last bit of remaining valueless material.

DESERT PLACER GEOLOGY

The chances of finding a hotspot out in the desert, or in some other dry region, are probably just as good or as your chances of finding a hotspot in the watersheds of the gold-bearing mountainous areas. These chances are pretty good, providing that you are willing to spend the time, study and work that is necessary to implement a good sampling plan.

Probably your best bet is to start off with a “Where to Find Gold” book and study the geological reports which apply to the area(s) of your interest. There has been some small-scale mining activity out in the dry regions. Much of it was lode mining, but some placer activity took place, as well. A good portion of prior activity is recorded information today. It can be of great value to you to know where gold has already been found. It is almost a sure thing that the areas which were once worked for gold at a profit were not entirely worked out. They might be worked again with today’s modern equipment at a profit. Any area which has once proven to pay in gold values is a good generalized area to do some sampling activity to see if additional pay-dirt can be found.

The desert areas were pretty-much left alone by the large-scale mining activities of earlier times because of the accessibility problem. Often, during earlier times, there was not enough water to sustain life, much less to process gold-bearing material.

But desert prospector should not limit him or herself to only the once-proven areas. Most of the desert regions have gone pretty-much untouched by past (effective) sampling activity because of accessibility problems, lack of water, and not having adequate equipment to do the job up until recent years. So the desert prospector has access to a lot of ground, and there are not that many competitors to worry about.

A single large rain or wind storm can change the entire face of the desert in just a few hours. There is very little undergrowth in these areas to prevent a good-sized rain storm from causing an incredible amount of erosion. And so you hear all the old-timers’ stories of finding bonanza-sized gold deposits, marking their position, going out after tools and supplies, and then returning to find the desert entirely changed and the bonanza apparently gone. Undoubtedly, some of these treasure stories are true. After all, many of those old-timers had gold to go along with their stories. Many of them spent the rest of their lives looking for their “lost gold mine.”

All of the placer geology concerning wet areas also applies to desert placer deposits (most which were developed during wet storm events). The same remains true of eluvial deposits-which is the gold that has weathered from a lode and been swept some distance away by the forces of nature. Eluvial deposits in the deserts (called “Bajada placers”) tend to spread out much more widely, and in different directions. This is because they are usually not eroding down the side of a steep mountainous slope. Therefore, they are sometimes a little more difficult to trace back to their original lodes. But it can be done. The answer is to do lots of sampling.

History has shown that one of the best locations to look for gold is where the hills meet the desert and fan out. This is where the water slows down during flood storms and drops gold in the gullies and washes. There also are likely to be more gold traps further up the hillside.

When doing generalized sampling in the desert, concentrate much of your activities in the washed-out areas, where natural erosion has cut through the sediments and created a concentration of heavier materials. Dry-washes, dry streambeds and canyons are good for this. Get an eye for the terrain, looking over the high points and the low points to get an idea of where the water flows during large flood storms. Areas where the greatest amount of erosion has taken place are areas where the highest concentration of gold values might be found. Remember that we are looking at many thousands of years of erosive impacts.

Bedrock will be exposed in some low areas, as in canyons and dry washes. These are ideal places for you to get into the lowest stratum of material-where the largest concentrations of gold values are often found. Large and small canyons have been formed by many years of erosion and are likely spots to find paying quantities of gold.

Caliche is cement-like false bedrock which is commonly found in desert placer areas.(photo USGS)

The desert and dry areas also commonly have a “false bedrock” layer specifically called “caliche.” Sometimes (often), this caliche layer is only a foot or two thick. In some areas, gold is concentrated along the caliche, just like on top of bedrock.

After a storm in the desert, in some places you can find small pockets of gold in the gravel traps, under rocks and under boulders which rest on top of the caliche. Sometimes the gold is pounded directly into the caliche and needs to be removed with a pick or crevice tool. Caliche layers which are close to the surface allow small-scale dry-washing operations to be economically feasible, because of the lesser amount of gravel and material which needs to be shoveled off the gold deposits.

Streambed material can be recognized by the smooth water-worn rocks. Anywhere in gold country, where streambed material is present, is a prime area to be doing some preliminary sampling. Such material indicates that it has been exposed to a substantial amount of running water. This means concentrating activity took place with those same materials. It is possible that the material was once washed out of an ancient river.

However, gravel and material does not need to be water-worn to carry gold in the desert areas. Rough and angular gravel, which has not been greatly affected by water, also sometimes carries gold in volume amounts. Testing is the key.

Sometimes it can be worthwhile to do some sampling in the different layers of desert material when they are present and exposed. Gold concentrations in and between flood layers can happen even more in the desert. This is because of the flash floods which can occur there.

Sometimes substantial gold concentrations can be found just beneath boulders which rest upon bedrock, or up in a layer above bedrock.

When you find a gold deposit in a dry area, whether on bedrock or the caliche, you will want to thoroughly clean the underlying surface upon which the gold is resting. Seldom will you visually see gold in dry placer material-even when there is a lot of gold present. Use a whisk broom or vack machine to clean all of the loose material. Sometimes, it is also productive to break up the surface of the caliche or bedrock with a pick or other crevicing tool.

Occasionally, in dry washes, you can actually see stringers of black sand along the bedrock or caliche-especially directly after a storm. You can sometimes do exceptionally well by following these stringers and digging out the concentrated gravel traps. Do not forget to test the roots from trees and other vegetation in such areas. Vegetation requires a certain amount of mineralization to grow. Roots can grow in and around high-grade gold deposits. I have heard of single roots which have been dug up and produced as much as three ounces of gold!

Some electronic prospectors use their metal detectors to trace concentrations of black sand. Then they follow up by testing the areas which produce the strongest reads from their detectors.

Some desert areas, like Quartzsite, Arizona, also have gold just lying around anywhere-even on top of the ground. Such places are excellent for electronic prospecting and dry-washing. The deserts of Australia are famous for this. I have a number of friends who have been very successful in the Nevada deserts, using metal detectors to recover large numbers of nuggets, some very large, directly off the surface of dry desert ground.

If you find a piece of gold on the surface of a dry placer area, it is likely that there are more pieces of gold in the immediate area. Electronic prospectors call these areas “patches.” Gold generally does not travel alone-unless it was dropped there by mistake.

Sand dunes in the desert are usually not very productive. This is because they mainly consist of lighter-weight sands that were deposited there by the wind. However, sometimes the wind can blow off the lighter-weight sands from a particular location, leaving the heavier materials exposed behind. This is similar to what happens after a big storm at the gold beaches. This is something that should be watched for.

When prospecting around in the dry areas, when you encounter tailing piles from past dry-washing operations, it might be worthwhile to do some raking of the tailings and scan around with a metal detector. Sometimes old tailing piles can be productive enough to run them through a modern dry-washer.

 

 

BY MICHAEL WARREN

 

 

Old-Map

The Oak of the Golden Dream sits beside a quiet stream in what is now known as Placerita Canyon. It was here that gold was first discovered in California, clinging to the roots of some wild onions dug up one March afternoon by Francisco Lopez, a local rancher. The year was 1842, six years before gold was found at Sutter’s Mill.

Lopez’ discovery sparked California’s first gold rush. Since then, thousands of miners have picked and panned the San Gabriel Mountains north of Los Angeles, some continuing to the present day. The years have worn away most evidence of this forgotten gold rush. But hidden high up in quiet canyons or on treacherous granite ridges, one can still find reminders of a time when hardy souls extracted a living from these mountains.

Placerita Canyon State Park, three miles east of Newhall, is where it all got started. The Oak of the Golden Dream, a twisted old California Live Oak, stands at the west-end of the park, north of the highway. Some old machinery and a small museum mark the site where early prospectors took $80,000 in gold out of this canyon (no panning is allowed anymore within the park boundaries). The small stream runs only a few months each year and was bone dry this past July, the fifth straight year of drought in the state.

Lack of water was a major obstacle for the placer miners of the 19th century. The Mexicans who did most of the mining in Placerita and nearby canyons used dry panning to winnow out the gold, but the process was not efficient. Even so, the placer gold soon gave out. By 1870 the streambeds yielded little to prospectors.

But soon they were locating the veins where the placers originated. Copper ore was discovered while surveying for a railroad to connect Los Angeles with the Mojave Desert in 1853; but at the time, it was not considered important. It was not until 1861 that miners went back after the copper – and then discovered, in the process, silver and gold.

Thus began the boom in Soledad Canyon. The town of Soledad, also known as Ravenna, quickly sprang to life. Then it died, then it revived again. By 1868, it had enough residents that a U.S. post office came to town. Through the lean years, the Mexican miners kept things going. They weren’t of the boom mentality that kept their Anglo counterparts hopping from one bonanza to the next.

The Soledad lode mines proved much more profitable than early placer operations. Mines such as the Governor, the Don, and the Red Rover boomed and busted for almost a century until they went dormant in the early 1950’s. When the Governor mine shut down in 1942, it had produced more than $1.5 million–making it the best-paying mine in Los Angeles County. Not much mining continues in the old Soledad District these days, but the sites have left a permanent mark on the hills.

Lu Anne Warren, author’s wife, standing in front of the entrance to the Monte Cristo Mine

: Lu Anne Warren, author's wife, standing in front of the entrance to the Monte Cristo Mine The Legendary Monte Cristo find in Placerita Canyon was not the first discovery of gold in California, either. It was simply the first documented claim. Rumors of gold circulated as far back as the late 1700’s. One legend surrounds the Lost Padres Mine, which was supposed to have been connected with Mission San Fernando. Vast amounts of gold were said to exist at Mill Creek.

The legend can’t be verified, but gold does exist high up in Big Tujunga Canyon near Mill Creek. A small gold rush hit this area in the late 1880’s, and some mining continues to this day. Some speculate that the Lost Padres Mine would later become known as the Monte Cristo, the best producer of the Big Tujunga mines.

The two-mile hike up to Monte Cristo mine from Monte Cristo Campground on Angeles Forest Highway takes you past the Black Crow mine (only the foundation of two buildings are left) and the Black Cargo–a small operation that is continuing today. About a half-mile beyond is the Monte Cristo, which has also been worked recently.

The Monte Cristo, which is not posted, looks like its tenants moved out just last week. Several abandoned houses sit in the junction of two creeks. Old machinery is strewn about, including an old rusted-out, bullet-riddled car. Little of it appears to date back to the mine’s peak years of 1923-1928. Fairly new-looking beer cans suggest the area is populated on the week-ends, if not worked occasionally.

The mine was first discovered by Mexicans and perhaps Indians before that. The first documented, full scale mining began around 1893 and was abandoned shortly thereafter. In 1895, Captain Elbridge Fuller took over the mine. Fuller seemed to have difficulty keeping partners. He either sold them out or drove them away. One of them was found dead with his head blown off. Fuller abandoned the mine after two decades.

Bur Fuller moved too soon, it seems; because the next owner turned the mine into a success. Fred Carlisle developed six tunnels and made $70,000 during 1927. But Carlisle too, saw the ore run low. The mine closed in 1942 by order of the War Production Board.

Close to Home: Probably the most accessible of the old mines, is the Dawn Mine, in Millard Canyon just above the Altadena. It’s a five-mile round trip hike, involving a lot of boulder hopping and stream crossings. A worthwhile hike even without a mine at the end, it takes you through a beautiful riparian woodland, a wonderful seclusion remarkable for its proximity to the city below.

Gold was found here in 1895 and the mine was worked into the early 1950’s. Like most of the mines of the San Gabriels, it was more ambitious than profitable. The main shaft, which ran 1,200 feet into the mountain, is still open (short assays can be found nearby on the canyon walls). Old machinery litters the canyon bottom, some of it crushed like aluminum cans between the boulders. The foundation of the miner’s cabin is located a quarter-mile below the mine. One of its owners built a trail up the canyon to connect with the Mount Lowe Railway, a marvelously-engineered railroad that ran from Altadena to Mt. Lowe in the early part of this century.

“The Dawn Mine followed the pattern of the great majority of mining ventures in the San Gabriels: initial promise, hard work, diminishing returns, and abandonment,” writes John w. Robinson, an expert on the San Gabriel Mountains.

For anyone still looking for gold in the San Gabriel Mountains, the most likely place to find it is in and around the East Fork of the San Gabriel River. The most profitable mining in the mountains was done here, and it’s still the best spot for recreational-scale mining.

Little is left of the placer operations here; but at one time, this canyon teemed with miners. The East Fork was the best-producing district of the San Gabriel Mountains. As much as $13 million in gold was recovered here. Once again, water was a major problem. But this time, it was the flood waters that periodically wiped out operations–one reason so little is left of the streambed operations.

The small town of Eldoradoville was wiped out in 1859. Eldoradoville was a tough little town of three stores and half a dozen saloons. One miner claimed he made more money by sluicing the sawdust from the floor of a local saloon, than by mining the canyon. The place was rebuilt after a flood and then prornptly destroyed again in 1862. There is a campground there now, a more conservative gamble against nature.

Hydraulic mining began in the canyon around 1871 and closed down in 1874 due to legal difficulties. Nevertheless, the energy and creativity invested into establishing hydraulic works, and the amount of gold extracted by it, was tremendous. The two major operators each extracted many thousands of dollars per month in gold by hosing down the canyon walls.

The East Fork saw a boom during the Great Depression. Eldoradoville became, “Hooverville,” a town of cardboard shacks populated by jobless men trying to make some money by gold panning. The town was washed away in a flood during 1938. Along with the town, all of the road was washed away except for a bridge that arches 250 feet above the East Fork Narrows. It’s called “The Bridge to Nowhere.”

Profitable lode mining was done on the rugged mountains above the East Fork, as well. The largest mine was the Big Horn. The spectacular mill remains in good shape. But recent exploration has begun again in the mine and the road is fenced, blocking any view of the mill.

The mine was discovered in 1895 by Charles Vincent who was hunting big-horn sheep. During its peak years of 1903-1906, $40,000 in gold was extracted–about $100,000 in all. Mining continued sporadically until the early 1940’s. Occasional exploratory work has been done since, .and the mine is currently owned by Centurion Gold Ltd.

The four mile round trip hike from Vincent Gap to the mine yields a terrific view of the East Fork watershed. Mt. Baldyand Iron Mountain fill the view to the southeast. Even the ridge that connects the peaks–some of the most rugged terrain in the San Gabriels was mined in the early part of this century .The Allison, the Baldora, the Gold Dollar, the Eagle and the Stanley-Miller are in this vicinity. Only the Allison is reasonably accessible, but even it requires one of the toughest hikes in the mountains. Not much gold was taken out of any of them the Allison extracted about $50,000 from the mountain. These high-altitude mines are monuments more of courage than business acumen.

There ~gold in the San Gabriel Mountains, but so far the hills have beaten back the prospectors. Until a new bonanza is discovered, California’s first gold rush remains only a colorful page in history.

For more information. The best resources available on historical mining in the San Gabriel Mountains are by John W. Robinson. See his books, Mines of the East Fork, Mines of the San Gabriels, and his trail guide Trails of the Angeles. Also check out Where to Find Gold in Southern California by James Klein

 
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This story first appeared in Gold & Treasure Hunter Magazine
Sep/Oct, 1996 on Page 14. This issue is still available! Click here.

By Dave McCracken

“Having the Gold Mining Adventure of a Lifetime!”

Dave & Alley

Author’s note: This story is dedicated to Alan Norton (Alley), the lead underwater mining specialist who participated in this project. Under very difficult conditions, Alan made most of the key dives which enabled us to make this a very successful venture. Alan lost part of his ear to a hungry fish one day; and the following day, Alan was making a key sampling dive again because we needed him to. There are very few people I know, if any, with more courage, dedication and enthusiasm to successfully complete a difficult mission than Alan.First came several Toyota Land Cruisers. Then, a couple of Isuzu Troopers, followed by a number of small pickup trucks. These were just in front of two large Russian troop carriers, all filled with armed troops. They came in on us fast, carrying along a big cloud of dust from the dirt road. Even before the vehicles came to a stop, soldiers were jumping out of trucks and running out to secure perimeter positions. They were carrying AK-47 machine guns, M-79 grenade launchers and Chinese rockets. I had seen these guys before. I had fought with them, and I had fought against them. They had that unmistakable look in their eyes. They would kill with little or no provocation.

Once the perimeter was secured, three generals stepped out of their Land Cruisers and enthusiastically approached us, their personal bodyguards close behind. The generals looked friendly. Their bodyguards looked seriously unfriendly! The generals, whom we had not met until now, hurried right up to me and each of my men and gave us big hugs, hand shakes and slaps on the back, like we were long lost sons. The bodyguards stood there with machine guns pointed in our general direction, doing what they were supposed to do to ward off any potential menacing threat to their leaders–which, by the way, never crossed our minds. We did the natural thing; we acted like long lost sons!

We had not been in Cambodia even for one hour before we were packed into Land Cruisers of our own and driven to Kampong Saom on the coast–which was almost half way across Cambodia. The end of the dry season had caused the water levels in the Mekong River to drop so low that deep-water ships were no longer delivering cargo to Cambodia’s capital, Phnom Penh. Therefore, it was necessary for us to go to Cambodia’s only other deep-water port in Kampong Saom to take delivery of five full ocean shipping containers of mining and additional equipment, supplies, boats and vehicles that had been shipped over there from America to support our project.

Since nothing happens immediately in Cambodia, we ended up spending about a week at a gorgeous beach while waiting for the shipping containers to be released by Cambodian Customs. Our hosts were taking good care of us. The hotel was comfortable, the beer was cold and the crab meat was freshly cooked on the beach–and it was all we could eat. In fact, we were just about getting bored. That’s when the generals showed up.

Isn’t it amazing how fast boredom can turn to fear? After hugs and handshakes, the generals agreed it was time for target practice. They had their bodyguards throwing beer cans out into the water so they could shoot at the cans. Pretty soon, lots of people were shooting at them. The few civilians that had been enjoying the beach scurried off quickly and respectfully. Everyone was laughing and having a good time except us. We were laughing, but not sure if we were going to be the next targets! It was all too much at once. We didn’t even know these people and they were all enthusiastically shooting their guns off. We were surrounded!

Pretty soon, one of the generals handed me some kind of machine gun I had never seen before and challenged me to shoot a fresh beer can. It was the only beer can remaining on the beach! This was a tough position for me to be in; those guys were not the best shots. I calculated whether I should try to out-shoot them, which might cause the generals a loss of face in front of their men, or to miss the can and perhaps lose their respect? On an impulse, I clicked the machine gun over to full automatic and fired a short burst to find a mark, adjusted slightly, and hit the can, knocking it up into the air on the second burst. No one had used automatic fire–probably to conserve bullets. All the generals burst out in a roar of laughter, followed by all their men. Deciding to quit while I was ahead, I handed the machine gun back to the general with the clip still half-full of bullets. That was the end of target practice and the beginning of my very warm friendship with that general. About a week later in Phnom Penh, this general and his very kind family, with great ceremony, adopted me as their number-one son.

The beach was just the beginning of 60 days of non-stop adventure which took me and three of my men from one end of Cambodia to the other in search of gold and valuable gems.

As it turned out, the generals were directly involved with this exploration project–which, by the way, was the first precious metal exploration project in Cambodia since the United Nations returned control of the country to a Cambodian coalition government in late 1991. During the course of the project, it became abundantly clear that our presence, and our successful venture, was very important to these generals and the Cambodian government. Cambodia is just getting back on its feet after decades of war and agony. The country is hungry for capital investment from the east and west. Successful ventures such as ours would help facilitate that.

Our project took place in northeastern Cambodia on one of the three main tributaries of the Mekong River. We were hired to help this operation put its suction dredging equipment into production and to help find high-grade mineral deposits.

The area is remote. In fact, it is the same area America bombed in the early 1970’s (with B-52’s) to prevent the Viet Cong from moving supplies on that portion of the Ho Chi Minh Trail. You just would not believe the number of bomb craters; I have never seen anything like it. In fact, up until the time of our project, I don’t believe a single bulldozer had visited that section of Cambodia since we bombed it! While these conditions probably never did slow down the Viet Cong very much, they certainly did slow us Americans down a lot! It took literally weeks for us to transport our equipment to the work-site. Trucks and trailers would disappear into craters and then come back out, one after the other, like a big roller coaster ride–only in slow motion–for hundreds of miles! It was one of the most amazing things I have ever seen!

All the while, our security troops were worried about being ambushed by Khmer Rouge rebels–roving bands which were still occasionally shooting up taxis, burning bridges, robbing various business establishments and causing other acts of terror around the countryside. Our generals were very concerned to make sure there were no embarrassments on this operation. Therefore, they sent along a 300-man military force to provide security. Each of us was also assigned several personal body guards. They also issued each of my men and me our own machine guns–which we gladly took. You kind of feel naked without a weapon when everyone else is walking around with some kind of heavy fire power! Here follows some video segments that I captured of our interaction with our bodyguards and some of the troops that were assigned to our project:

By the way, the people of Cambodia are the kindest-natured people I have ever associated with. Everyone is very polite and friendly. Unless it is worth dying over, you never see an argument in Cambodia! During the entire 60 days of our project, there was not a single person I smiled at that I did not receive a heartfelt and sincere smile in return. They seem to genuinely like Americans. In fact, any product or item that says Made in America is in great demand in Cambodia–especially hats and insignia which carry American flags and symbols.

One night, we had to make an emergency dash through rebel-held territory so that we could meet a production deadline. We were driving like madmen through bomb craters, up and down, with grenade launchers and machine guns hanging out windows. Our security people were very concerned we would be ambushed. Better to be safe than sorry, I suppose. But, I never saw any direct sign of danger. Even so, the eminent concern–with guns and grenades pointed out windows, with everyone on moment-to-moment alert–created a charged atmosphere which we usually only experience on television in America.

We received incredible hospitality from native villagers in every community that we passed through or stopped to visit. Many villagers had never seen white men before. You have to remember that Cambodia, for the most part, lost an entire generation of people to the Khmer Rouge regime. Locals told us the ratio of women to men in Cambodia is five to one, because the men were either killed in war or murdered. That ratio is about how it appeared to me.

The equipment we sent there to use for sampling took a very heavy beating during the trip across Cambodia. The axles we mounted on the dredge platforms were badly bent from being dragged through hundreds of craters, and there was quite a lot of other damage, too. So we found ourselves staged for about a week in the last town before we would reach the river. This was a place where various supplies and services were still available. There, my men and I supervised final repairs and preparations for our sampling program. It is very challenging to do this sort of thing in an environment where most of your helpers do not think the same as you do, and do not speak any of your language:

Between the delays at Customs, the painstaking trip across war-torn Cambodia with the equipment, and the time we had to spend repairing gear at the final staging area, we only had about 2 weeks remaining to accomplish what we went to Cambodia for in the first place. A final distance to the river of 35 kilometers does not sound like very far; but in Cambodia, where anything and everything can go wrong; this last 22 miles still seemed like a long way to go. Even so, there was a lot of excitement when we had everything ready and began our final journey to the river from the last bit of civilization that we would see. The following video segments demonstrate the excitement that we were all feeling to finally get started on our dredge sampling program:

Along the way to the river, we started seeing lots of diggings alongside the road. We thought the holes were water wells at first, because they were perfectly round and uniformly about 2 ½ feet in diameter. Then we realized they must have been something else, because there were so many, and they were positioned so closely together. We stopped to take a look as soon as we saw some locals actively working inside one of the holes. These turned out to be sapphire miners! They were digging about 10 meters down to bedrock and recovering handfuls of pretty blue stones from the bottom gravels. These miners were selling their gemstones for mere pennies (Me and my guys were buying!). We found out these miners were from the Cambodian hill tribes; jungle dwellers that pretty-much are the same as they have been for hundreds or thousands of years. A number of humanitarian groups are now present in Cambodia attempting to prevent the modern world from impacting too dramatically upon these ancient tribal people. The following video segment captured some dialog that we had with a few of the sapphire miners. It presents a good example of how simple and kind the people are from the Cambodian hill tribes:

Immediately upon our arrival at the river, we realized that we had 2 serious problems to overcome. The first was that there was about a 10-meter drop from the bank down to the active river. There was no ramp or other simple way to launch the 10-inch dredge and special recovery platform that we brought with us for this job. Not wanting to use our security force for this, we immediately set out to hire around 30 men from the local hill tribe village to dig a ramp. That exercise took about 6 days to accomplish. So we were not going to have use of the big dredge until the final week of our project.

Our second serious problem was that the (sizable) river water was running mud-brown. We did not know it at the time, but there was some active dam construction happening upstream in Vietnam. The ongoing construction was turning the river to mud-water. That meant that we were not going to have any visibility underwater. There is a way to get the work done in dirty water; but besides the serious safety problems associated with dredging blind on the bottom of deep tropical rivers, you have to do everything by feel. This slows you down to just a fraction of what you can accomplish with some underwater visibility. This was going to be a difficult mission to accomplish!

All travel on the river from our base camp had to be accomplished by boat. The boat that we arranged broke down on our first trip downriver to survey the area. As it was just before dark on our return to camp, and the mechanical problem seemed pretty serious, we actually started making plans to sleep on a sand bar that was located out in the middle of the river, maybe 5 miles away from our camp. With no dinner and no shelter from the mosquitoes, it was a pretty bleak feeling out there. I captured the following video segment just as our guide was suggesting that we spend the night there on the sand bar. Fortunately, they got the boat motor operating just as darkness was almost complete. It sure felt good to finally arrive back at camp that night where there was a hot meal and perfectly good tent waiting for each of us:

While we were doing our initial survey downriver, we came upon a local river mining operation that was using a long-handled (about 15 feet long) shovel, suspended by a floating platform made of bamboo. This dredge was being used to excavate sand off the bottom of the river. The locals called this a “Vietnam dredge,” because the river mining technology had been imported by miners across the border in Vietnam. Almost the entire dredge was made out of materials from the jungle. Even the lines being used to tie off the dredge out in the river were made from jungle vines. The only part of the dredge we could see that was from our modern world was the head of the shovel. That looked to be fashioned from the car hood of a bombed-out jeep. This river location was part of the Ho Chi Minh trail. So there were plenty of bombed-out jeeps around, and some ruined Vietnamese tanks, too. In fact, there was a lot of painful history here!

Author and several team-members trying out a “Vietnam Dredge,” made from bamboo, which local miners use to bring gold off the bottom of the river.

Upon discovery of the local river mining program, we immediately took the opportunity to make friends with the local miners and the elders of their village. This is standard procedure anytime we are performing an preliminary evaluation in a new area. While their methods might sometimes be somewhat primitive compared to ours, I have found more often than not that hundreds (or thousands) of years of local mining experience has given the miners who occupy an area a strong perception of where the richest gold areas are located. We did not have much time remaining to make a rich discovery for our clients. Any head start the locals could give us would surely be a welcome development! Ultimately, the locals told us that their dredge was positioned along the strongest line of gold that they knew of in the river. That was a big help!

To get an idea of how much gold they were talking about, we accepted their invitation to go down and operate their Vietnamese dredge for a little while. The following video segment captured my guys running the local production equipment. It worked by pushing the shovel down into the sand, and then using a make-shift windless to raise the river-bottom material to the surface. There, local wooden gold pans were used to process the material:

While the local miners were recovering a fair amount of gold from the river-bottom sand deposits, their success did not appear to help us very much. This was because we wanted to sample for the high-grade gold deposits which are almost always located at the bottom of hard-packed streambed layers. In working their Vietnamese dredge for awhile, it did not take very long for us to realize that the long-handled shovel would not penetrate the hard-packed streambed material that was under the sand. Too bad!

5″ Pro-Mack Sampling Dredge

Still, knowing where local miners were supporting their villages with gold from the river gave us a starting point. The following day, we moved two 5-inch special sampling dredges onto the river some distance downstream from where the locals were mining, but directly in line with them so that we had a better chance of sampling on the strongest path of gold in the river

My guys were initially quite challenged by going down into the pitch blackness along the bottom of a muddy, tropical river. Because there is zero visibility down there, everything must be done by feel. This is not easy to do, because your imagination cranks up into overdrive about what might be lingering around down there to bite or eat you in the dark. Remember those horrific nightmares you had when you were a kid? That stuff doesn’t ever go away. The terror is still present; it is just buried. Going by yourself down to the bottom of a tropical river in total darkness, and having to feel your way around to figure out what is down there, energizes all you nightmarish fears right back to the surface. It is difficult to do what you are supposed to do down there with all this internal fear playing out inside of you! It takes courage and a lot of discipline.

So my guys challenged themselves with acquiring some preliminary sample results using the 5-inch dredges, while I was pulling the 10-inch dredge together and installing a special shaker table in the base camp that we would be needing to process large samples. The table needed to be anchored in concrete. All of this took several days. Time was running out!

On the second day of sampling, our lead diver, Alley Norton, touched down in some hard-pack and came up with a pretty good showing of gold. The following day, I encouraged Ally to go back down and open up the hole (get a bigger sample). We had to keep dredgers separated while sampling, to avoid someone getting smacked with a cobble being tossed in the dark. There simply is no way to tell where anyone else is when you are dredging in muddy water. Alley’s hard work and enthusiasm paid off. Considering how small his sample actually was because of the dirty water, he recovered a lot of gold! We had located high-grade!

I captured these following video segments towards the end of the third day of sampling:

As we had less than a week remaining to accomplish our mission, we all focused the next several days placing the 10-inch dredge and platform into the water. The local help had completed our launch ramp according to plan. Wow, was that a lot of work! Once the big dredge and recovery system were floating in the river, we still had to dial it all in to get it working right. This was particularly important with the sophisticated recovery system that we had brought along for this job.

Before opening up Alley’s discovery with a production sample, we needed to make sure the recovery system was working right. This all took another two days, because the large volume of sand from the bottom of the river was overwhelming the gravel pump that was supposed to transfer classified material to the recovery system. This problem required us to get very creative in the middle of the jungle. Through some trial and error, we constructed several water blasters to inject water into the feed of the gravel pump. This made sure that enough water was going into the feed to keep sand from packing up in there. While all of this took up valuable time, we had to get the big dredging system fully functioning before using it to perform the final production samples in Alley’s rich discovery

We only had 2 days remaining on the project when we finally floated the big dredge over Alley’s rich discovery. Talking about racing against the clock! So while Alley went down in 6 meters of underwater darkness to suck up the sample, I stayed up on deck to fine tune the dredge’s recovery system. You can only put one diver down on a big, powerful dredge in dark water. So our other guys helped where it was needed. Alley spent several hours opening up a large hole through about 2 meters of loose sand. Our plan was to first pump most of the sand off the hard-packed streambed material where Alley had found the gold. Then we were planning to flush the sand completely out of the recovery system before dredging up the pay-dirt. This was to minimize gold losses because of too much sand overwhelming the system at once.

We were making good progress on our plan. But about half way through the day, Alley climbed back onto the dredge with a lot of blood flowing down the right side of his head and face. A pretty sizable chunk of his right ear was missing and it was bleeding profusely! Blood was actually squirting out with the pulse of his heart! He said while operating the dredge’s suction nozzle on the bottom of the river, it felt like a submerged log with rough bark brushed by his head, scraping his ear. When he reached up to touch where the pain was coming from, he could feel that a part of his ear was gone. That’s when he came to the surface. Seeing all that blood and the bite out of Alley’s ear was very dramatic for everyone that was present.

Back at camp, we bandaged Alley up as best we could. We always bring a substantial medical kit with us on these projects. We applied antibiotics just to be safe. Alley said the pain was not too bad. He was mostly worried about how ugly it was all going to look later. I would have been worried about that, too! There wasn’t anything else we were going to do about that situation out in the jungle, though. So we decided to set aside that problem for another time. We were going to depart Cambodia in a few days, anyway.

Collectively, my guys and I decided it was wise to not do any more diving in the river until we found out what bit Alley. Whatever it was, there was a chance that we could still salvage the sampling project by wearing more protective gear while underwater. We still had one more day available to perform a final production sample!

As none of our bodyguards or the other military guys in camp seemed to have any idea what bit Alley, we decided to drive the motor boat up to the hill tribe village where the Vietnamese dredge was operating. We had already made friends with the villagers and elders there. Once there, we removed the bandage from Alley’s ear to show the elders, and they immediately knew what bit him. They told us that there is a fresh water blow fish that lives on clams at the bottom of the river. Apparently, this type of fish must have come alongside Alan’s head; and in the very poor visibility, thought his ear was a clam. One bite and there it went. The villagers assured us we would have no further problem with that fish if we started wearing hoods, gloves and full face helmets in the river while it was muddy.

Afterwards, we heard the story of one of our military men bathing naked in the river and losing his vital organ. Apparently, the man had just been married several weeks before. Luckily, we had been taking our showers up on the bank!

When we arrived at their village, the local people were busy preparing for a “grand celebration” that was to take place that evening. All of us were invited to attend, and it would have been impolite for us to decline their kind hospitality. The celebration turned out to be a funeral ceremony for one of their important elders who had died 3 years before. I have seen similar traditions in Madagascar, where the big celebration of someone’s life happens by the whole village several years after the person dies. These hill tribe people were busy decorating a whole shrine that would be dedicated to the person, carving all sorts of symbols relating to the important things the person lived through. Interestingly, the biggest symbols I recognized were American military helicopters and B-52 bombers. No doubt, the later part of the Vietnam war must have been a very traumatic time for these very simple hill tribe villages, with the Viet Cong using their river for a highway, and the Americans dropping thousands of tons of bombs all around.

These people seemed nothing but pleased to have us Americans present, so we accepted their invitation to participate in their party that evening. Indeed, the party turned out to be one of the most interesting events I have ever been part of. A center covered circle had been built for the people who wanted to express their grief over the loss of a loved one. Inside that area, there were around 20 people who were crying and almost howling in deep grief. Outside the circle, the rest of the village paraded round and round in a dance in joyous celebration of the person’s life.

My guys and I jumped in with the outer group. They were beating on different-sounding chimes to make their traditional music. The sound was so interesting that I captured it on tape. The occasion was something I am sure that none of us will ever forget. We were honored that they allowed us to participate in such an important tribal event. They were honored that we joined in with them. It was a wonderful bonding experience between us and remote villagers of the deep jungles of Cambodia. The following video segment and audio segment capture some of our hill tribe friends as they were preparing for the party, and then capture some of the music and feelings that we shared together that evening:

Hill Tribe Music:

The following morning found our team back on the 10-inch dredge, preparing to perform one last production sample. This was our last day to accomplish what we went there to do. So much effort and money had been invested to transport this fantastic equipment halfway across the world, through some of the most difficult circumstances on the planet; only to finally arrive on our last day right over top of what appeared to be a very rich gold deposit.

It was so important that we get the best possible production sample, Alley insisted that he take the first dive. He had started the sample on the previous morning, so he knew the layout of the hole in the total darkness of the river bottom. Total darkness down there would have required either of my other two guys to spend valuable time figuring out what Ally had already done. As this gold deposit was really Ally’s personal discovery, we agreed that he would take the first dive of the day to open up his hole. I would spend that time dialing in the recovery system as well as I could. Then I would finish the sample during the afternoon with a second long dive. My other two guys were content to support us from the surface. I don’t think they were quite over the emotional shock of Alley’s blood and guts from the day before. Who could blame them?

As I knew this would be a memorable occasion that none of us would ever forget, I captured some video of Alley bravely overcoming his fears and going back down into the deep black hole that attacked him on the previous day, something very few people would do. You will see from the following video segments how good the production dredging equipment was that we managed to place on top of that rich gold deposit. I believe the recovery system was the most sophisticated that had ever been used with a suction dredge up until that time. It was truly a miracle that we ever got the equipment there, or that we found such a high-grade gold deposit under those difficult conditions. With all that we had been through, in my world, there was no other choice but to perform that final production sample:

After a few hours of diving, Alley came to the surface; because his ear was throbbing in so much pain, that he said he could no longer focus on what needed to be done on the bottom of the river. By then, the recovery system was dialed in as well as we were going to get it. So I suited-up and went down into Alley’s deep, black hole. This was actually my first dive on this entire project. During the week or so that we had been on the river, there were just too many other things that needed to be accomplished which only I could do to bring everything together in time for this final production sample. So there I was, taking the last and most important dive of the whole project!

I will never forget in military jump school, the first time I bailed out of an airplane. It was one of those situations where I really did not have much of a choice. But looking way down there at the ground made jumping feel totally wrong. My body did not want to do it. So it was necessary for me to flick some internal emotional switch, override my natural instincts, and just force the body to make the jump. Going down into deep muddy water is much the same; the body does not want to do it!

I have actually done quite a few dredging projects where it has been necessary to perform the underwater work in muddy water. It is never easy! Especially when the water is deep! It was around 6 meters just to the bottom of this dirty river. That is a long way to go down in the dark. I worked my way down there slowly by following the suction hose, which is where I knew that Alley had left off. When I reached the suction nozzle, I rotated my body around it in a circle, feeling around with my legs and feet to try and find Alley’s dredge hole. Letting go of the nozzle was something I was not prepared to do, because it was the only thing that gave me a reference point down there in the total darkness. Also, feeling around tentatively with steel-tipped work boots felt safer than reaching out in the dark with my hands!

I soon found that Alley’s hole was just off to one side of the nozzle. Experienced dredger that he is, Alley knew better than to leave an unattended suction nozzle down inside of a dredge hole in the sand. The walls never stop sliding in on sand-excavations or loose gravel. If you leave a suction nozzle down inside of one, within just a short time, the suction nozzle and hose will be overwhelmed and buried. That would have been the end of this project. There was not enough time remaining to dig a hose out of the sand in the dark!

Once I found Alley’s hole, I memorized where the suction nozzle was positioned several feet away, and then I followed the edge of the hole all the way around to get some idea how big it was. This was the hard part, because it meant that I had to reach out and feel everything with my hands. All that blood pouring down the side of Alley’s face the day before was vividly on my mind! There were creatures down there with serious teeth! Here is where I had to flick another fear-switch off and just do the work. These fear switches are not really turned off. They are just suspended. I speak from bad experience. Depending upon how many of your internal fear-switches are in suspension, it just takes one small event to turn them all back on into nightmarish panic and terror. I have been there. It is not fun!

Reaching out meant feeling out as far as I could outside the outer edge of Alley’s hole to make sure there were no boulders up there that would roll in on me in the dark. I did not find any. Slowly but surely, I explored all of Alley’s hole by feel. It was pretty big; maybe 30 feet in diameter at the surface, funneling down to a center point about 2 meters deep. Alley had pumped a lot of sand! Before I went down, he told me that he touched down on the hard-pack streambed at the bottom of his hole, but that the sand kept sliding in on him. So he had not been able to get a sample of the hard-pack, yet. This was for me to do!

I invested about 2 hours into taking a sizable cut off the front and one side of Alley’s hole, working the sand back step-by-step in the darkness. I wanted to uncover enough surface area of the hard-pack as possible. This was so that further sand-slides would not prevent me from getting a good sample of the hard-pack. With time, I started uncovering the hard-pack. This is where the loose sand met the cobbles, boulders and gravel that were tightly compacted together. Though I could not see it, it felt just like the hard-pack we dredge along our properties in California.

While the dredge was plenty powerful enough to pull apart the compacted streambed material, my progress was slow. This is because I could not see the oversized rocks that had to be moved out of the way, and I could not put my hands out in front of the nozzle in the dark without getting them hurtfully banged up. Mainly, I just poked around down there in the dark to suck up anything that would go up the nozzle. Each time a loose cobble would block the nozzle opening, I would wrestle it off and put it behind me. It was not long before I had more loose cobbles behind me than I could manage. It was too far to throw them out of the hole, and trying to pack them out would have caused more sand to slide in. So I just juggled everything around down there the best I could, determined to get as much of that hard-pack up the nozzle as possible. Ultimately, my progress became overwhelmed by loose cobbles in the hole and sand sliding in from the sides. I had not reached bedrock, but I did get a fair sample of the material that Alley had touched down upon with the 5-inch dredge several days before. By my measurements in the dark, I estimate that I sampled less than a cubic meter of hard-packed material. That was all we were going to get under those difficult circumstances. It was a good feeling to finish what we had traveled so far to do.

The guys turned the dredge down when I reached the surface. I had to wait at the ladder for the longest time to allow my eyes to adjust to the bright sunny day. As I was waiting, my guys were making a lot of enthusiastic noise about visible gold in the recovery system. When I finally was able to see again, I climbed up onto the dredge to see that the entire recovery system was inundated with a thick layer of small golden flakes. It was, by far, the most gold I have ever seen recovered out of such a small volume of gravel. This place was rich!

We had just enough time before dark to run our concentrates over the shaker table back at camp. Everyone there experienced an incredible feeling of pride. Under very difficult circumstances, against all odds, we stuck it out right until the last hour to make this project a success. Watching all that rich gold flow across the shaker table had all of us in awe about how rich this river is. Who would have ever guessed? Right there on the Ho Chi Minh trail! While I am sorry to have missed capturing the gold-laden recovery system on the dredge, I was able to recover myself enough to capture the following video segment of the final clean-up. To put it in perspective, our small sample caused that shaker table to flow gold like that for a full 15 minutes!

We returned to civilization the following morning, and departed Cambodia a few days later.

Follow ups:

A short time later, our clients met with some serious misfortune by aligning themselves with the losing side in a power struggle over who would control the government in Cambodia. While they survived the events, they have been banned from the country forever.

Shortly after my clients found themselves in big trouble, all of the equipment and supplies we sent over (that they paid for in advance) were taken away. The only thing remaining there today that shows we were ever even present is part of a steel frame from one of the large floatation platforms. Everything else is long gone.

The wars in Cambodia are now long over. The people there are very friendly. You do not see guns there anymore. People are focused on getting ahead in business. They want to be like America. The government is trying hard to attract foreign investment.

Nothing since our project has been done to develop the deposit that we located. Although the government of Cambodia has offered to make an exploration license available, I have yet to raise the high-risk capital necessary to go back over and do something about what we found

I made a special trip back to the site of our discovery 2 years ago. The bad roads have been replaced with a highway! Schools have been built in the village communities. The people out there were happy to see me. Most importantly, dam construction in Viet Nam was finished and the river was running clear!

While I was out there, I hired a local boat to take me downriver to see if anyone was doing anything with our deposit. Nobody was there. Even the Viet Nam dredges were gone! It appears that my guys and I were the only ones whoever really understood the significance of what we found there. Local miners cannot access the rich material using their technology. With clear water, we could process hundreds of times more hard-pack in a day than what I sampled down there in the dark.

The following video segment was taken in the very place where the earlier segment showed us operating the dredge:

Alley and his brother are now managing a successful concrete business in Phoenix, Arizona. He never did anything to fix the bite out of his ear. Now he says the tattered look gives him personality and character. Since nobody will believe he had his ear nearly bitten off by a clam-eating fish while prospecting for gold at the bottom of a muddy river in the jungles of Cambodia in the middle of a war along the ancient Ho Chi Minh trail, he now just tells people that his ear was bitten off by someone while fighting in a bar on the north side of Phoenix. That’s already more adventure than most people can handle!

Note: This story was pulled together from the non-proprietary portion of an initial report from a preliminary evaluation of a potential production dredging project in Northeastern Cambodia. The opportunity to do something with this prospect still exists.

 

 

By Dave McCracken

Talking about putting yourself way out there beyond where you should not be!

Dave Mack

Actually, I had no business diving in that cave with the equipment I that was using. The gear was old and used heavily in my dredging program. The breathing regulator leaked out of the side. The mouth piece rubber was no longer being held on by a band or plastic wire tie. My underwater flashlight was not working well. It would flicker on and off again, making it necessary to bang it on something to get it to come back on. I simply did not think the whole thing through! I have been diving all my life, and I should have known better. But I do have an excuse, it was treasure fever that was clouding my judgment, and I had it bad.

It all started when an acquaintance of ours told us about the treasure in Hall City Cave. My brother Brian and I had been dredging in a very rich pay-streak, three to four ounces of beautiful gold every day with a six inch dredge in the middle of the cold winter months. We were only dredging about four hours a day. The gold was just pouring in. Then a big storm came in which knocked us out of the water for about a week. That is when the old man told us about the treasure which the Indians hid in the cave.


Mark Keene and Ivan Jackovich looking for
treasure in the same cave a few years later

As the story goes, some time during the late 1800’s a few renegade Indians attacked and killed the miners of a small hydraulic mining operation near the town of Hayfork, in Trinity County, in northern California. While the mining operation might have been small, they were doing very well. The Indians apparently stole about one hundred pounds of mostly nugget-gold from the dead miners.

Since the Indians were on foot, and also carrying a very heavy load, it did not take long for the posse to catch up with them. In fact, as a last ditch effort to get away, the Indians stashed the gold somewhere so they could move faster. When the posse caught up with the Indians, only the Indians knew where the gold was. The men in the posse told the Indians that they would not be hung for their crimes if they would tell where they hid the gold. The Indians told the posse that they had hidden the gold in Hall City Cave. Then they were promptly hung right on the spot.

As it turns out, Hall City Cave has a deep, submerged cavern at the back of the cave. The cavern is said to be bottomless, because no one apparently has ever been able to get to the bottom. And of course, not the posse, or anyone else, ever found the gold. Did the Indians hide the gold somewhere in the cave? Did they just dump it into the bottomless cavern to get rid of it? Did they have some secret hiding place in the cave, perhaps underwater? Or did they hide the gold somewhere else?

As the story goes, during more recent years, there have been several deaths in the cave. These were drownings, as scuba divers have tried unsuccessfully to recover the hidden gold nuggets. There is a strong legend that powerful Indian spirits remain in the cave to guard the treasure, to scare away or kill anyone trying to recover it. The old man told us the story. He believed that if anyone could recover the gold, it was us; because of our superior skill, our experience, and our integrity. Especially our integrity, since the old man wanted an equal third of the treasure if we found it. He had the information and the maps; we were to provide the necessary equipment and do the actual diving part of the operation. “What the heck,” we decided, we were not doing anything else productive; just watching the rain and waiting for the river to slow down and clear up.

The old man drove; and other than a few logs crossing the seldom-used old logging dirt roads, and a little snow, we got to the cave with little trouble. It only took about an hour to pack the diving gear up the semi-steep hill to the cave. The cave itself was not very large. It was about seven feet tall in places, ten or fifteen feet in others. Most of the cave was wide enough to walk through, except one spot where it was necessary to squeeze through sideways. The cave did not extend very deep into the mountain, only about forty or fifty feet. The water-filled pool at the back of the cave looked very deep as we shined our flashlights into the water.

The cave was dark and gloomy. Menacing spirits were dancing in the shadows as we shined our flashlights around the cave while moving the equipment into place. The small area of the cave succeeded in giving us a closed-in feeling. Something about the atmosphere inside the cave was very wrong. We all had the same feeling that what we were doing was not right, like we were trying to steal something that did not properly belong to us. There was an unmistakable feeling of menacing gloom inside the cave, the feeling like we were in big trouble and that we should get out. All of us felt the gloom!

In fact, the feeling was so strong, we went outside and had a short discussion, reaffirming our determination for being there; agreeing that the gold was indeed ours if we were able to recover it; and also resolving that if disembodied beings were in fact making us feel so nervous, then it was all the more likely that the gold was hidden in this place. And, of course, it was also okay with the others because it was me that was going to do the diving. I was the most experienced.

The water in the back of the cave was crystal clear and ice cold. I chose earlier to use my dry-suit, and I took fifteen pounds of lead off my weight belt to make me less heavy in the water. In dredging, it is necessary to weight yourself heavily to the bottom of the river. In diving, especially cave diving, you want to achieve neutral buoyancy so you can swim up or down as you like. My problem was that my weights were in 15-pound increments.

To take another 15 pounds off would make me too light. To leave it on made me sink rather quickly. It was a choice I had to make. How easy it is to simply make a decision. Then you are stuck with the consequences! I chose to go heavy. I figured it would be better to not have to fight my way down into the deep hole against positive buoyancy.

The pool of water at the back of the cave was the surface of what turned out to be a round shaft which extended deep down into the earth at almost a vertical angle. The shaft looked to be around six feet in diameter. Shining my flashlight down, I could tell that it was deep. I could also see what appeared to be additional chambers which extended off the top of the main shaft. “Perhaps this was an old mine?” No, I remember thinking, there were no tailings or waste dumps outside the cave. “It must be limestone,” I thought, remembering the limestone caves near Del Loma which the Indians used to conduct raids from the small town of Denny up on the New River, through 20 miles of underground connected caverns. “This underwater cave could be bottomless,” I thought.

Rather than wear the scuba tank on the first dive, I felt it would be safer to use the fifty-foot airline that I had brought along. I attached one end of the airline to my scuba tank, which was to stay at the surface. The other end attached to my breathing regulator, which went into my mouth. This way, I could do a preliminary exploration without having to worry about getting caught up in tight corners with a bulky scuba tank on my back. The airline also gave me a direct link to the surface. Rope does not generally work very well for this sort of thing underwater, because it has a tendency to get tangled around vital things.

I just wanted to do a preliminary look around without getting too far away from the surface; which in this case, was going to be no more than fifty feet. Then I could think about putting the tank on my back and venturing further into the darkness. As it turned out in the end, this was a decision I would be glad I made.

We only had one scuba tank; and since my brother was not experienced using scuba equipment anyway, I had to settle for him acting as a tender holding a flashlight at the surface. Besides, I had the only underwater flashlight, so there was not very much he was going to do for me if I did get into trouble. It was pitch dark down there!

Of course, my flashlight started giving me trouble as soon as I started down into the main shaft. My depth gauge had just told me I was only fifteen feet into the hole when the light quit the first time. I stopped quietly in the darkness for a moment, listening, trying to get more comfortable in my surroundings. “What was that slight rumbling noise?” It was very light. Was it the echo of our own movements and noise in the cave, perhaps my air bubbles against the upper wall of the cave? No, it sounded too deep and far away for that. It almost sounded like the heavy beating of drums from far away. It was a very distant sound. I found myself looking into the darkness, trying to figure out if the sound was really there at all.

I tapped the light a few times along the side to bring it back to life and continued deeper into the shaft. As I descended, I passed several openings that extended upwards off the main shaft. “Good places to hide the gold, maybe,” I thought to myself as I went by them. When my depth gauge read 35 feet, I stopped and looked down the shaft. The water was perfectly clear. With the bright light, I could see well beyond the remaining fifteen feet that my airline was going to allow me. The shaft continued to extend at the same straight angle into the darkness, giving the perception of endlessness. The angle was so steep that if they threw it in this main shaft, the gold would not have stopped until it hit bottom. “No way to reach that without a scuba tank on my back,” I thought.

Looking up at that point, I noticed that there was a smaller shaft extending off the top of the main shaft. This one was only about 3 ½ feet in diameter.

“Better to check out the close quarters of these smaller, upper shafts without the tank on my back,” I decided, as I jumped up into the smaller opening above me. I was wearing my dredging boots; and because I was weighted slightly heavy, it was necessary to span the perimeter of the almost diagonal shaft and use my legs against the sides of the shaft to climb upward. While doing this, I managed somehow to keep the flashlight pointed in an upward direction. Looking up, all I could see was darkness. I was hoping to find the water’s surface and a hidden open chamber with a treasure of gold nuggets inside…

I climbed upward until I felt the familiar tugging of my airline, telling me that I had reached as far as it was going to allow me. At that point, while breathing in, I got a full mouth of water! Getting a mouth full of water can often happen when gold dredging in fast water. When your regulator is positioned just right (or wrong?) into a strong water current, the rubber exhaust valve will sometimes allow water to flow into the final stage of the regulator. This will give you a mouth full of water if you happen to be breathing in at the time.

This happens often to me, because I mostly dredge in fast water. My body just accepts it as a normal routine. I simply use whatever is left in my lungs to blow the water out of the exhaust ports. Then, I carefully take in my next breath. There is always a certain amount of undivided attention that goes with taking this next breath; because if it is more water, it is necessary to act quickly to avoid drowning! Almost always, though, I get nice clean air on the first intake after blowing the water out of the regulator. That’s why it was such a surprising shock to me in that cave when I got a second mouth full of water!

Now I had no air in my lungs at all, and I whipped the flashlight around just in time to see the regulator sink out of sight into the darkness. I still had the rubber mouthpiece in my mouth. Pulling on the airline the way I did must have made the rubber mouthpiece slip off the regulator. How could I be so stupid to dive without fixing it first? The realization of my position was terrifying. My body was screaming for air, and I was a long way from getting any. “Do I go down 15 feet to the main shaft and then climb another 35 feet to the surface? I don’t think I can possibly make it that far! Or, do I go towards the surface in the small shaft in hopes of finding air up there?” These were my only two choices.

I don’t even remember turning around in the cave. Going down was not physically difficult because I was weighted heavy. But as I went deeper into the cave, the increased pressure of the greater depth compressed my lungs even further, making my body turn into a panicked, psychotic animal. My body was screaming to turn around and go back up the small shaft, to do anything, anything to get air!

Have you ever had anyone hold your head underwater, or hold you down while blocking your nose and mouth from taking in air? If you have, then you have some idea of what I was going through. It took every bit of discipline I could master to reach the bottom of the small shaft.

The momentum, and the extra lead on my belt caused me to slip even further down into the main shaft. My lungs were a vacuum; it felt like they were squeezed flat. This feeling and the panic were one and the same. There was no discipline left. Just a mad scramble to get up the shaft. It was difficult. The tunnel was almost straight up, and I was wondering if I might have made a mistake and gotten into the wrong shaft!

The extra lead on my belt was pulling me back down. My feet were slipping on the smooth rock surface, and there were no hand holds. I was making progress, but it was painfully slow. I found myself watching the action in slow motion from outside the body. Inch by inch the body was moving, but I was not going to make it in time. The panic and desperation were kind of a far off feeling now. And then the flashlight flicked off!

It was the sound of drums after all, and they were louder now, much louder, all around me, in fact. The monotones, rhythmic pounding of the drums had an alluring, hypnotic effect upon me. It was a wonderful feeling to be a part of the ceremony. No, I was the ceremony! This was not something that was foreign to me or something that came from the outside. It was something I have always had with me and chose not to look at. The distant feeling of enthusiasm, and a feeling of greatness took over as I watched my fellow warrior-brothers dancing and leaping with wondrous strength, glory and bravery around the fire. They were singing “Hey Yey Yey Yey, Hey Yey Yey Yey,” to the beat of the drum. And I realized with exhilaration that this was a place where effort, emotion and thought all came together as one; a place which transcends time. This was my place, and the realization brought about the enthusiasm to jump in and give myself completely to the eternal dance around the fire…

“The light went out.” The voice from another world said.
“What?” said another voice.
“He was just about to surface and I think he lost his light again,” said the strangely familiar voice, with obvious concern.
“Huh?” I remember asking myself. “What is this?” And the sudden realization of the sadness this would cause to my brother, and to my family and close friends. “Not this way” I told myself; and looking up, I realized that it was not a fire I was looking at. It was my brother’s flashlight at the surface, just above me.

It was not very hard to scramble up the last few feet to the surface. I came out of the water like a madman, gasping for air. The first breath was vastly painful, the second not so bad. I was left the rest of that day, and the next, with mixed emotions; the feeling that I was simply happy to be alive, and also the feeling that I had been robbed of something important. “You O.K. Bro?”, asked my brother.

Yeah, I was going to be O.K. I spent the next hour or so diving in the shallow parts of the cave. This was not the first time I have come close to drowning, or the second for that matter. I prefer to try and stay in the near vicinity until the shock wears off. Kind of like getting back on the horse again immediately after it has thrown you, I guess.

And the treasure? It is probably still there! You can have it if you can get it! I know now that it certainly does not belong to me, if only for the reason that I am not going back after it. I will get my nuggets the hard way; I’ll stick to gold dredging!

 

 
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This story first appeared in Gold & Treasure Hunter Magazine May/Jun, 1993 on Page 45. This issue is still available! Click here.

By Dave McCracken

Classification is necessary to increase the amount of smaller particles of gold that you will trap in your recovery system.

Dave Mack

 

It takes more water velocity to move larger-sized material than it does to move the smaller-sized material through a sluice box. Yet, to the degree that the water velocity over a sluice box is increased, there may be a loss of fine gold recovery. Or, to the degree the water velocity over a sluice box is slowed down, there is likely to be an increase in fine gold recovery–as long as there is still enough flow over the box to keep the riffles concentrating.

When larger rocks are pushed through a sluice box by water force, they also create greater turbulence behind the riffles as they pass over, which may cause an additional loss of fine gold.

To improve gold recovery, it is common practice to run material through a screen to classify out the larger rocks before running the material through the recovery-portion of a sluice box. In this way, less water velocity is needed through the box, which allows for a more orderly flow, and an increase in fine gold recovery. The action of screening materials is called “classification.” Materials which have been passed through a classification screen are called “classified materials.” The following video segment demonstrates this very important point:

The size and depth of riffles within a sluice box play an important part of this. A slower water flow might not keep a deeper riffle concentrating. A greater water flow can sometimes “boil-out” a lower-profile riffle. So as water flow is slowed down to catch finer-sized gold, it is generally necessary to use shorter riffles.

Half-inch mesh screen is commonly used for primary classification in small and medium-sized sluicing operations, because the screen is large enough to allow classification to take place quickly, yet no materials greater than half-inch in size will get into the sluice. Therefore a slower-velocity of water can be directed through the box, and fine gold recovery will be improved.

Classification for a sluicing operation can be done in any number of ways. One is to place a piece of strong half-inch mesh screen over a bucket, and shovel or pour through the screen into the bucket while sweeping the larger material off to the side. Once the bucket is filled with classified material, it can be poured into the sluice box at a uniform rate. It is better to not dump the whole bucket into the sluice all at once! This is because too much material is likely to overload the riffles and cause a loss of gold recovery.

In a situation where it is necessary to haul material a short distance to the sluice box, sometimes it is easiest to classify the material directly into a wheelbarrow and transfer only the classified material to the sluice.

Perhaps one of the best screening methods is to build a classification device that you can shovel into, and which will stand directly over the top of, and drop the classified materials into, the head of your sluice box.

The device should be built with the screen set at an angle. This way, larger material is helped to roll off of the screen as the pay-dirt is shoveled onto it. Smaller materials should fall through the screen and be directed into the head of your sluice box. This is actually a miniature model of the big classifiers used by large-scale heavy equipment bench-mining operations. A classification device such as this is rather easy and economical to build and will speed up a production-sluicing operation while screening is being done to improve gold recovery.

Any recovery system will only recover gold effectively down to a certain size-range. Most gold particles smaller in size than that will be lost with the tailings. Classification is one effective way of increasing the amount of gold that will be recovered out of the material that will be processed. As demonstrated in this following video segment, this is especially true of suction dredges; because dredges are able to increase the volume of production over other types of hand-mining activity.

Here is a substantial explanation of the system which we have developed to effectively recover more fine gold on our conventional suction dredges. It combines two classification screens to more-effectively separate material-feed into three size-fractions, each which is directed into a different recovery system. The smallest gold particles (which are most difficult to recover) are directed into low-profile riffles along the bottom of the sluice box which have long been proven to be very effective at trapping fine gold.

 

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