At least eight of the mines boasted total production in excess of 1,000,000 ounces. Overall, hardrock mining accounted for about 60% of the gold produced in the Mother Lode and Sierra Foothills. The most serious problem of mining the gold veins themselves was that quartz, the host ore, was an extremely hard mineral.
Gold mining has greatly increased Cu concentration in the environment which upon release binds to particles of organic matter, clay minerals and sesquioxides leading to great accumulation in the soil . Copper exists in two states, oxidized state Cu, and reduced state, Cu.
The average level of gold that is found in soil is about 5 ppb. This can be used as a background level of gold content anything above that is rated as an anomaly. In practice soil tests are taken on a grid pattern; a good size to work with is a plot of land 400 by 400 m with samples taken every hundred meters.
About 15 percent of the gold produced in the United States has come from mining other metallic ores. Where base metals such as copper, lead, and zinc are deposited, either in veins or as scattered mineral grains, minor amounts of gold are commonly deposited with them.