Lode or Placer: What Difference Does It Make?
September 2014 by Keith BowenThis explains the large difference in particle sizes between placers and hydrothermal lode deposits, but also means that while the mining may be similar in some cases, the sampling and recovery techniques are usually quite different.
In processing gold, silver and other valuable ores, the minerals containing the values, such as metallic gold, silver-bearing sulfides or other minerals, must be freed from the surrounding host rock before those valuable minerals can be captured.
All these decisions and more depend on the richness of a claim—something that is determined by sampling. But sampling isn’t cheap, and even collecting the samples can be more difficult than it appears on the surface.
Prospectors often wonder why gold deposits in veins like it does. Why is one vein rich while another is barren, even though they are only a few hundred feet apart?
I love to dry wash old nugget patches found by detector operators, and I have found my fair share of gold dry washing those areas. I have also found a few nuggets using a detector on the bedrock exposed by dry washing the patches.
Once I have established the presence of gold in the sample, I collect five-gallon bucket quantities of the rock material for processing back at my shop.
The first step in my recovery process after milling the ore to the desired size is to table it. On this particular ore, I get good results milling it to minus 100 mesh.
Another little gem of equipment he built was a nifty sample splitter. In order to get accurate assays, you need to have really good, representative samples for the assayer to process.
The Bawl Mill • Ask the Experts • Ask the Experts • Taking on the EPA, Sasquatch, Ratchilla and Gold Dredging • Gully Prospecting and Mining • Wilfley Tables—Repair, Rebuild & Set Up • Designing and Evaluating Placer Gold Recovery Plants • Finding Streams of Gold • This is Why You Check Your Tailings • New Rules to Impact the Lease/Buy Decision • There's a First Time for Everyone • Appeals Court OKs Permits for Upper Peninsula Mine • Melman on Gold & Silver • Mining Stock Quotes and Mineral & Metal Prices