How to Set Up and Use a Gold Sluice Box
With gold prospecting, trial and error is important to developing technique. It may be hard to find gold, but not because of the sluice setup. If the material you are shoveling onto the sluice opening is all being washed away, you need a smaller angle of submersion. If nothing is being washed away, you need a lower angle. Somewhere in between these extremes is the best adjustment. This article will cover how to set up a sluice along with a bit of its history.
Stream Sluice Set Up
Water should enter the wide end of the sluice. It is frequently made of metal, but might also be of wood or plastic. It is the wide end and quickly tapers to the width of your riffled material. Weighting down your sluice may be necessary. If the stream current is strong, the sluice will be carried downstream without added weight. I usually place stones on the edge of the sluice to hold it down. The water should flow over the riffles quickly, but not so quickly that the material is all washed away. Adjustments up and down will quickly give you a reasonable angle for gold retrieval. You can also sample what is held in the riffles with each adjustment to get an idea of what angle produces the greatest amount of flake. In general, the more water flowing through the sluice (rate of speed of the water), the less the angle of inclination. The slower the stream, the greater the angle. How big the stream or river is has nothing to do with it.
And another thing to consider. If the stream or creek is really ripping, you can build a dam out of rocks on the up end (behind the flare). That will slow the flow enough for you to successfully adjust the sluice up and down in the water. If the stream is running really fast, it won't matter much how to adjust the sluice - any angle will result in all of your material being washed out.
It is assumed that the reader knows how to pan, as the sediment from a sluice box must be panned after it is gathered. Just as the motion you use to pan gold comes with practice and the watching of heavy sediment gathering at the down edge of the pan, so with practice the speed of the water and the adjustment of the box angle will become second nature.
Sluice Factoid #1
A sluice (from the Dutch sluis") is a water channel controlled at its head by a gate. A mill race, leet, flume, penstock, or lade, is a sluice channelling water toward a water mill. The terms sluice, sluice gate, knife gate, and slide gate are used interchangeably in the water and waste water control industry. - WIKIPEDIA
Placing material at the flared end and as close to the end as you can, the material will wash through the sluice from beginning to end. If half a shovel full works, do that. Dropping a huge amount on a narrow flare will just block the water from trailing down the sluice. You will get a feeling for this, too. I wait until everything has run down the sluice before putting another shovel on. You will notice the water getting muddy soon after dropping your shovel full. As the water streams down the sluice, it clears rapidly. This is another way to determine when to reapply material.
Riffles have been engineered to stop the flow of gold as it runs down the sluice. Since gold is very heavy, it will be stopped by the riffles as other lighter material passes through and then back into the stream. The pressure behind the riffles slows water and holds material behind. This hindering gives time for gold to settle out. Your gold and lead and other "heavies" will be held there. This process continues over and over again. How much material is behind the riffles determines when you will want to clean them.
Some sluices are submerged in a bucket of water to rinse off the heavies from the riffles. Some models allow you to pop out guards that hold the "moss". Rinse the moss in a bucket of clean water until all the material held is removed. I use a plastic tub to wash my riffles, but a big bucket works too. Of course, the bucket has to be wider than the sluice or moss. You can get Sterilite containers (61cm x 47cm x 40cm) at Walmart.
Sometimes carpeting is used as moss, but at any rate, rinse continuously, as you don't want to leave gold flake behind. I have even seen blanket or course cloth used under the riffles to catch the finest of gold.
You replace the miners moss with the bracket back into the sluice (just the reverse of taking the sluice apart). The concentrates that are in the tub contain any gold that might be there. You want to take this material and pan it or run it through some other fine gold device like a blue bowl. You can also use sluices designated as fine gold recovery. They usually come with a recirculating pump. The key to success is mostly the adjustment of your sluice. It isn't much of a chore as it may seem. If I can do it, you can too!
Hungarian Riffle Sluice
Factoid #2 - Proper Amount of Material Behind a Riffle
Riffles about half full of material indicate the right amount of water flow.
A Bit of History
The Chinese are frequently cited as having introduced the sluice box to gold mining during the 1849 California Gold Rush. However, the use of devices to slow down the flow of water over pay dirt has gone on for centuries.
"There are many Bronze age (depending on the geographic area, 3000 BC to 1000 BC) gold objects, Ireland and Spain of note, with several well known sources possible. The Romans used hydraulic mining methods, such as hushing and ground sluicing on a large scale to extract gold from large alluvial (loose sediment) deposits, such as those at Las Medulas." - Wikipedia
A refinement on the typical riffle is attributed to the Hungarians (eastern Europeans) during the 1849 gold rush. The refinement known as the Hungarian riffle box is shown below. The riffle would retain more of the heavy sediment referred to as pay dirt.
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© 2016 John R Wilsdon