Did you know that fine gold recovery usually makes up for the majority of gold found by small time prospectors? Its much more plentiful and it’s usually found in places that are easier to get to. The problem with fine gold is that its so small and improperly set up sluice boxes can let it pass through unintentionally. To remedy the problem you must be aware of the main factors involved. Water speed and volume are critical! Even in a poorly designed sluice, if you have the volume and speed of water dialed in you will still catch gold more effectively than using a pro high end sluice that’s set up wrong. Furthermore, the angle at which the sluice boxes lay are also very important. The angle will effect the speed of the water as it travels down as well as how fast the sluice is able to clean itself out. If the angle is too shallow bigger rocks and clay chunks can settle on or around the riffles and cause turbulence in the water that will effectively kill the back eddie action created by the riffles. It will cause you to lose gold! Those points being the most critical, next is the construction and design of your sluice. It’s ability to catch gold and specifically fine gold are decided by and far by the designs of the riffles and or catch mat systems.
Finding the appropriate water flow and speed for your circumstances is absolutely essential. It can be tricky and might require you to block the flow of water from the inlet of your sluice, or feed extra water in. This can be accomplished by making a small dam with rocks in the creek or river bed. Depending on where you’re prospecting this could be considered a violation of your local Fish and Game laws so be aware of them. Chances are, if moving rocks in the stream bed is considered a violation so is using a sluice box. Make sure you know the laws!!!
The more water volume the better and generally speaking it doesn’t hurt to fill the sluice with water right to the top of the sides if you can. A good recommended minimum depth is about 2 inches. Volume is usually separate from the speed of the water so you can adjust it easily by lowering the sluice into the water more or by finding deep spots in the creek bed that act as a funnel for your sluice.
The proper flow can be judged by using small pebbles or a handful of sand. Drop it in the inlet of your sluice and watch as it flows through. all but the heaviest particles should be washed clean within 3 to 5 seconds depending on the length of your sluice. 3 is a bit quick but will allow for much faster production of concentrates at the cost of losing some fine gold. 5 is a tad long or just about right depending on the coarseness of the material you’re sluicing. You should be catching lots of fine gold at that speed but at the risk of larger rocks getting caught in the riffles and disrupting the flow. You can adjust the angles for fix that though.
When setting up a sluice the proper angle must be observed. It’s usually between 5 – 7 degrees of slope and should allow most round rocks and pebbles to pass through easily. You don’t want the material zipping through but rather kind of tumbling through slowly. An Ideal speed is for a larger rock to clear itself out within 3 to 5 seconds on a medium sized sluice box. Also remember that the angle effects the water speed as it travels down the sluice. Furthermore, sometimes it is impossible to achieve the right angles if the creek is very flat. In such a circumstance you may be required to create a make shift dam out of more rocks to raise the level of water on one side so you can feed it through your sluice. But that can be a lot of work and you’re usually better off trying to increase the speed of the water instead.
With the proper angle, water flow and speed set, it’s now time to actually use our sluice boxes!! Many people pre-screen their material before feeding it through the sluice. It’s a lot of work and a properly set up sluice does not need this. However, that being said, If you don’t pre screen or classify the material you will likely lose some fine gold. This problem can be helped by using a classifying screen over your sluice inlet as you shovel dirt in. I used an old dishwasher rack I found in the creek bed and set it in the inlet of my sluice box. the water washed through it and as I dump material in, it washes it down leaving the bigger rocks and clay chunks for me to easily throw out. It’s a great light weight solution that really speeds up my production. It’s also a much better alternative to dry screening the material right at the dig site then carrying it the 10+ feet to my sluice. You results may vary but at this point you should have a fairly good intuition about the possibility of losing gold.
Pulling your sluice out of the stream can be a tricky process and will inevitably lead to some gold being lost. It is highly recommended that as you go to remove the sluice for the water stream you place a bucket or pan at the end of it to catch whatever might get accidentally washed out. I’ve seen fouled up attempts at removing a sluice cause small chunks of gold to be washed clean back into the stream. Be very careful.
After that, clean up is a breeze and not to mention fun. You finally get to see how all your hard work paid off. It’s worth noting though if you’ve got one of the newer generation plastic sluices you often have the added benefit of an even easier clean up as well as a nice view of whats collecting during the sluicing process! The downside is the lower production ability.
Hopefully that should get any new prospector started! I hope you enjoyed my guide!
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