A good and efficient setup for capturing gold is important, but don’t overlook the fact that you first need to release the gold the mud and clay!
Importance of Separating out the Gold
Gold prospectors are always looking for new equipment that will help them recover the most gold that they can.
For a placer miner, there have been nice improvements over the past century. From old long-tom sluice boxes constructed of wood, to carpeted sluice boxes, to miner’s moss, and the newer rubber matting materials. The small-scale miner has the ability to recover more small gold than ever before.
One thing that should not be overlooked however, is that regardless of the type of matting that you are using you still need to release the gold from the dirt in order to capture it! A small particle of gold that is completely encompassed with clay or soil is simply not going to settle like it should. If you don’t wash your gravels well then you are going to lose gold.
Smaller Placer Operations
Some miners don’t put much effort into washing gravel. If you’re gravels are relatively “clean” then you may not need to. However, if you are processing dirt that is heavy in clays then you really need to wash those gravels if you want to get gold.
Let’s look at some examples. Most small-scale miners have used a sluice box. This is one of the most basic types of placer mining equipment, and only requires that the miner shovel gravel into the head of the box. The force of the water separates the gold from the lighter gravels and allows them to get captured into the riffles.
In many places, simply shoveling dirt into the sluice is all that is needed. You will get good recovery rates without any extra effort, which allows you to process even more gravel during a day of mining.
However, let’s say you are digging dirt and gravel from an ancient river channel. There are lots of heavy clays in the material that you are digging, and the dirt is dense and compacted. If you shovel this heavy material directly into the sluice, even some of the richest gold-bearing material is going to run right through the sluice and be lost forever.
This happens because the heavy clays don’t have time to break apart. When you shovel it into the head of the sluice, it only has about 3′ of riffles to break apart, release the gold, and settle behind the riffles. That 3′ is plenty IF the gold is already separated out, but if it’s still locked up in heavy clays then you are almost certain to miss it.
How to do prevent these losses? The simplest and cheapest way is to classify the material with sieves. This will not only help to bust up the clays, but it will also separate everything into like-size materials. This will add to the efficiency of your operations.
Larger Placer Operations
Simple hand-held classifiers and sieves are great for the small-scale prospector, but a larger operation that is moving yards of material is going to want something mechanized to do that work for them.
If water isn’t a limitation, then a trommel is a great piece of equipment to use. It is a rotating drum that contains pressurized jets of water that will effectively break apart clays and wash rocks. An efficient trommel setup is difficult to beat.
Commercial placer mining operations almost always use trommels in their wash plants. The larger rocks and gravel that is rejected will be washed perfectly clean, dense clays will be broken apart thoroughly, and efficient gold recovery is possible.
There are huge wash plants that cost hundreds of thousands of dollars to put together, but smaller operations can also use smaller trommels that will only cost a few thousand dollars. You will have to evaluate your own mining operation and decide if the added cost is worth the investment.
Keep in mind, depending on the size of motorized equipment you are using on your claim, you will likely need to get proper permitting in place. This process can take years if you are on federal lands, and it costs money too. All things to consider whenever you scale up an operation.
Washed Gravels and Sticky Riffles
Cleaning gravels is critical to the success of a placer mine. In some areas with very little clay it might not be necessary. The gold may separate easily, and a good sluice box setup will catch most of your gold. If you are dealing with heavy or cemented clays, then you’ve got to get it busted up before you can get that gold!
Once the gravel is clean and gold is released, then it’s up to you to adjust and tweak your mining equipment to maximize recovery. We have better equipment today that we’ve ever had in history. You can buy a variety of products that will have excellent gold recovery; the ability to capture extra-fine gold is especially nice. Miners can work ground that earlier mining equipment simply couldn’t trap the gold.