LEAF MINING

It is no mystery that the majority of sluice boxes are made from sheet aluminum, however, with all the different thicknesses and grades of our “AL” friend to choose from we should focus on maximum strength with minimum weight characteristics. Most companies that make aluminum sluice boxes don’t offer you a choice of alloyed materials to choose from but instead sell you whatever they’re buying in bulk at that time. The best way I can serve you is to offer these water chutes in light, medium and heavy-duty grades so you know what you’re buying before you purchase. As far as the alloy component goes I’ve chosen the longest wearing metal with the ductility that still allows it to take the bumps and bangs of moving your sluice along the stream or river bottom without puncturing it. Just for your information, some of the alloys the aluminum manufactures add to make your sluice box stronger are:

•             copper
•             magnesium
•             manganese
•             silicone
•             zinc
•             chromium
•             iron

And course I would never use cast materials in sluice box composition. I only use a heat-treated wrought sheet alloy. The heating removes stresses and uneven distortions that can occur when the aluminum is pressed at the time of manufacturing. Another plus that heat has to offer is a final hardening of the sheet material depending on the alloy base used when the aluminum batch was made. You wouldn’t like me much if I used pure aluminum in your sluice box. It would be as weak as papier-mâché [on a good day]. On the flipside, the pure stuff stays shiny for a long time so the crumpled mass that used to be a sluice would look pretty good for years to come.

Longevity with a lightweight construction is the aim. Once we have a solid box that will take some abuse we place the very effective capture media for the bulk of the length. The whole idea behind any capture media [i.e. miners moss, extruded nylon, riffle strips etc.] is to create multiple pressure zones where gold particles and flakes will become trapped as they drop out of the flow, based on their weight. The lighter “waste materials” [sand, gravels and mica] will be carried along with the water flow and out the end of the sluice.

All conventional sluice boxes work by gravity separation. Gold is heavier than granite, black sand [magnetite], quartz and all other rock types so dropping the heavier yellow metal away from these materials is possible. The real trick is to catch the really fine flour gold and still get rid of larger waste rocks. I will go on record here and say even a really bad, poorly designed sluice box will capture larger gold nuggets but it takes some careful planning and work to catch the fine stuff.

If the capture media or correctly sized riffles are the most important aspect in trapping gold then classification is definitely second. You can’t drop a fist sized boulder onto a sluice and expect the water to wash it through and still catch fine gold no matter what type of capture system you have. If you take that same size material and pre-size it so all fine and small sized sands are treated to the same correct water flow and capture systems, you will have success recovering gold. Obviously nuggets will be pre-sized and washed at a separate rate versus flour gold.

I think a big holdback for fast recovery in a production setup is a rapid way to size, wash and ultimately separate gold from waste rock. In fact, larger operations usually don’t have a special fine gold capture element anywhere in their sluice box. Some of the gold shows on TV show gold recovered in jars.  If you look there’s really no fine stuff anywhere to be seen. That means they are washing flour gold right through the system. It’s a real pity too. I estimate that they could enhance the recovery by 2 to 6 ounces per cleanup if they would capture this fine gold. All it takes is an add-on classifier and flour gold capture media. There is no restriction to their operation as the add-on classifier is flush with their sluice box and the materials with still be ejected at the end while capturing otherwise missed fine stuff. The secret to this is correct classification and capture media with water flow control. That’s where most miners get stuck. Understandably most gold supply companies don’t offer advanced fine gold sluice boxes that they take time to build and set up properly. If you were to take one of these units in the hands of an experience minor he would pull ounces of super fine gold out of a well worked sand bench or gravel bar. Conventional sluice boxes can’t touch it.

The idea behind miners moss was to provide a soluble, porous blanket to trap gold as it slowed because of this restriction in place. A tuned sluice won’t need any miners moss to catch the gold. Using a micro riffle system the waste sand would just wash through and leave the small gold behind. This also saves on hauling 5 gallon buckets of concentrates [mostly black sand] back home for further refinement. Now you have a smaller quantity of gold concentrates that is mostly fine gold and not magnetite, to clean up during the slower mining months.

The last thing I want to mention about sluice box design is vertical classification. This is where you can separate different sized materials that you feed into your gold system. Conventional sluice boxes use:

•             width and length
•             water flow
•             angle
•             size of riffles [usually more towards the front]
•             fine gold capture media [towards the end].

A vertical classification sluice has vertical layers that have a number of advantages over earlier conventional three stage sluice boxes. First, you will catch any large gold that a lot of systems pass right through their classifiers. Second, the bottom fine gold layer can be adjusted and tuned to trap micro fine gold without the use of miners moss or other similar all-encompassing slow water traps. Third, it is fast and requires no special handling of your gold bearing materials. In fact, I called this type of vertical set up “an apartment building for gold”.

Whatever type of sluice box you use you will find it much faster than just panning for gold. Just remember to classify your gold bearing materials before you feed into your sluice for best gold recovery.

Your sluice box-where gold really shines!