Silver is widely diffused but is rarely found in the native state.

Silver is originally as widespread as gold, occurring in nearly all of the volcanic rocks. Whereas gold remains unaltered by the action of the elements and is often carried long distances from its original place of occurrence, silver on the contrary is only to be found in the rocks where it originally occurs. When these rocks are broken down or worn away, the silver is either driven into new mineral combinations, or more often dissipated and lost. Silver, therefore, is only to be obtained by subterranean mining. Shafts are driven and the ore brought to the surface, and by use of various processes the silver is extracted, refined and made ready for commercial purposes.

An old process and one still employed extensively throughout Mexico where a large quantity of silver is produced, is to take the ore after it has been crushed or reduced to a fine mud or puddle and spread it about two feet deep over the floor of a large courtyard. Powered sulfate of copper is spread over the mass and then horses or mules are driven around in circle to tread the sulfate in and mix it thoroughly with the ore. After about one day