Of the thousands of mines, mining companies and processing operations in the US, most are abandoned and left few records. It can take a bit of detective work to find the Information that's still out there.
Relatively easy finds: Information about "famous" mines; property and claim records; regional production data and geology; mining districts; existence of a company and stock values
Difficult to find: Production figures, assay records for a specific mine; lists of employees; information about the equipment and surface operations; maps of underground workings.
1. Identify the location of the mine or the company's operations -- the more specific, the better.
2. Search using the mine/company's name. Look in:
3. Broaden your search. Use: