Most of us are familiar with the concept of “panning for gold” along scenic river banks of the Old West. Gold is also commonly found in rock quarries, especially in quartz, but sometimes with other minerals, including iron and manganese oxides, calcite, pyrite and sulfides. Crushing the rocks is not as simple as it seems, and separating the gold from the other minerals adds another element of difficulty.
1. Break large chunks of the rock into fist-sized pieces. Use a heavy-duty hand chisel for that task. Small chunks of rock can be handled more easily than large chunks and later placed in crushers .
2. A pulley-and-rope system is one of many crushing methods.
Crush the rock. Depending upon the volume of rock, your overall seriousness or stick-to-it-iveness you possess and the cost you want to expend for the array of crushing machines, various methods can be employed.
For the lowest cost option, use either a special hammer that fits securely into form-fitted metal containers holding chipped pieces that ordinarily would fly out or a pulley-and-rope system designed to raise and drop a heavy weight that chips away at the rocks.
For a higher cost option, use a hand stamper or small- jaw crusher . These are heavy cylinders of iron welded to a long rod then placed inside a pipe or tube that is just a bit larger than the diameter of the iron cylinder. The iron cylinder is picked up and dropped onto the rock, much in the manner of the old-time stamping mills.
For processing large quantities, such as hundreds of pounds of rock from mines, use a small, portable hammer and impact mill with electrical moving parts.
3. Conduct repeated screenings of the material crushed to a small size. Remove free gold already separated from the rock that won’t fall through a No. 16-20 screen mesh. Then the coarser rock can be returned to the crusher for further breakdown while the finer pieces won’t get in the way.
4. Separate gold from the crushed rock. Careful panning works for amounts fewer than 15 to 20 lbs. For large quantities of rock, use a more automated system such as a small shaking table.
5. Shiny metallic beads of mercury are a byproduct of gold amalgam.
Mix finely powdered gold-bearing rock with mercury. An adequate amount of mercury for basic processing is about 100g. That will dissolve gold within the rock to a form called gold amalgam. If you handle only a few gold quartz rocks, using mercury is not worth your time. Mercury, like all heavy metals, is toxic. So take the necessary precautions to avoid contact and ensure containment.
6. Separate the gold amalgam from unreacted mercury. Squeeze the crude amalgam through a small piece of chamois leather cloth. Shiny metallic beads of mercury will ooze through the leather, leaving the gold amalgam behind.