sentences:  The most productive silver district in Arizona that was mined primarily for silver was Tombstone in Cochise County, discovered in 1877.In 2006, all the silver mined in Arizona came as a byproduct of copper mining.Most of the silver produced in California has been a byproduct of mining other metals, such as copper (Copperopolis), tungsten (Pine Creek mine in Inyo County), or gold (Randsburg).