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As long as you are out there gold mining, please allow me to shave some time off your search for gold.
If most of the coarse gold near the surface has been found, (best estimates are 55 - 60%) there are only three choices left for the coarse stuff. Finding the hidden pockets where the gold lays, searching specific areas in the deserts and working high benches.
The Problem with Sluice Boxes
Many companies make claims on the total percentage of gold their sluice box will recover. This mainly refers to "fines" the box will catch. The difficulty I have with 98% of the sluice boxes out there is that they are built straight. There is no flow difference from the start to the finish. If we watch nature, she will vary a stream or river in many ways from rapids to waterfalls, bends, wide parts in the stream, back eddies, whirlpools and so on. With the High Production Sluice box we take advantage of a slowing current dropping more gold, just like in nature. The waterfall effect "scrubs" lighter rock from the low pressure zones leaving the gold behind.
Early Sluice Boxes
Early sluice boxes were nothing more than wood or fine clay troughs. Many different types of riffles were tried, stone, logs, grass, sticks, etc.
The pioneer prospectors found that a rough wooden sluice with raised wooden slats worked best and was easy to build. The principal behind the sluice box is the same no matter what design is used. Water carries gold laden gravels down the box and gravity ultimately separates the gold from the lighter rock and sand. In theory, it sounds simple, in practice, there is a little more to it.
Most sluice boxes use riffles or obstructions blocking free flow of gravel and sand from being washed out of the sluice box. These restrictions form low pressure pockets behind which gold will accumulate. Gold is 19 times heavier than water and approximately 16.5 times heavier than rock (quartz) so gravity separation can be accomplished. What makes sluicing for gold so challenging is that the size of rock versus the size of gold we are recovering is vastly different. The weight of a large pebble or rock will sometimes match that of a small nugget or piece of gold. More so, most of the gold we will recover will be flakes, small nuggets or worst case, flour gold. One way to solve this problem is to "pre size" our material before trying to separate it. This works down to a point, typically 1/8 of an inch. If we try to size our gravel and sand mixture much smaller than that we will end up jamming any screen or "classifier" we use.
So we can use another trick to capture very small gold particles. We flow all our materials over a ribbed carpet at low velocity (slow water flow) and the flour gold will become trapped in the uneven carpet pile.
This is one way to gravity separate gold from sand and gravel mix. There are definitely more.
By far the most common riffle used is called a "Hungarian Riffle" also known as a "Lazy L"
These riffles work up to a point but have a serious weakness when it comes to recovering fine gold. Most fine gold will wash right out of this style of sluice box.
Previous miners faced the same problems you will, separating the smaller gold flakes from the rock and sand. Early prospectors had limited tools and materials to work with so the would build very long sluice boxes (Long Tom Sluice) and many variations to try to catch finer gold.
There has been little serious advancement in sluice box technology since they were first created. It has taken me quite a while to perfect a very new type of High Production Sluice Box.
Each stage of this sluice is tailor made to recover:
- Small coarse gold pieces
- All flake gold
- Fine and flour gold
The key to this sluice box is High Production
I mentioned that the basis for the High Production Sluice Box was a prospector in Atlin B.C. I met in the mid 70's (as a kid). This placer miner used a mixture of techniques to make sluicing easier to recover more gold. Prospecting for gold was a hobby of his and he ended up buying a gold claim that was for sale in the late 60's from a miner that was broke. Deregulation of gold pricing followed in the early 70's and the value of gold bullion started to climb. There was a new gold craze on. Suddenly his gold claim was worth thousands (he paid $500). Atlin is a very wild Northwest corner of British Columbia. To say the place has alluvial deposits was an under statement. It looked like God had taken a fistful of gravel and rocks and dropped them over the earth. This whole area had been "turned over" by previous miners who had large sluice operations (steam bucket dredges). In addition there were areas of old lava flows which made prospecting for gold very challenging. Sniping with a gold pan was a good way to find "hotspots", but turning over an entire area was much more effective.
This prospector had build a new type of sluice box which was out producing other claims right around him. The mentality of the other miners around him was to recover as much coarse gold as possible and "leave the small stuff for immigrant miners". (That's the way it was). Of course these gold diggers made and used their own homemade gold sluice box based on earlier old designs. Wooden planks were the most common construction material used. Obviously it was a "build your own" environment.
But a dollar is still a dollar and all gold is still valuable. It is more a matter of how to easily get the gold to stick in your sluice than simply rush through only taking the easy coarse gold nuggets. The prospector had a very systematic approach on gold prospecting. He used a very old odd power shovel, like a back hoe and would dig down through the gold laden gravels and sands (more like boulders) until the length of this bucket was reached (approximately 7 1/2 feet). He would push this material through a crude classifier and then through his sluice box. After digging a wide area clear he would then dig down another step (7 1/2 feet). On one side of his claim he would hit bedrock (the side of the mountain). This is where he recovered most of the large gold nuggets from.
When he wasn't repairing his power bucket (which he was always doing) he would recover up to 11 ounces a day. Over half that amount of gold was fine stuff from flakes to flour gold. (Most traditional sluices had a type of material at the end of the sluice. Either matting or blankets would pick up the lighter gold.)
Of course the fine material was mixed with black sand and a few small garnets (he called rubies - hence the name Ruby Creek in Atlin).
All the fine stuff went into galvanized pails which were then stored in his crudely built shack.
During operation, the sluice was a thing of art and beauty to watch. The flow of water rose and fell following the contours on the bottom of the sluice. There were no riffles or riffle sections, just pockets between each raised portion of the box. These were low pressure zones in which gold would accumulate. He had this flow down to a science. Knowing just where to position and how high to make each rise.
At the end of each day he would clean up the sluice. It was always fun, kind of like bringing in a net that contained fish.
The gold was in bands in each pocket, going from coarse gold nuggets to flakes and finally to powder or flour gold near the end. At the start of each rise the color would go from solid yellow to a fine tapering band. This would happen at each raised portion until near the end of the sluice.
It was explained to me that the water flows direction change drove fine gold into the matting on the rise. I really didn't appreciate any of this wisdom, I only like cleaning up the sluice and exploring. Most of the other prospectors tolerated me on their claims as I wasn't panning gold I was just looking around and trying to have fun.
Anyway, that is where I was first exposed to the High Production Sluice Box.
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