Hundreds of scanned USGS files ("dockets") on mineral exploration projects in Arizona are now online for free download. They are part of a collection of 5,000 such files from all over the country, including a few hundred from Arizona. [right, number of dockets per county in Arizona]
This looks to be a real treasure trove of materials to sort through.
The USGS announcement summarizes the project:
Congress enacted the Defense Production Act in 1950 to provide funding and support for the exploration and development of critical mineral resources. From 1950 to 1974, three Department of the Interior agencies carried out this mission. Contracts with mine owners provided financial assistance for mineral exploration on a joint-participation basis. These contracts are documented in more than 5,000 “dockets” now archived online by the U.S. Geological Survey. This archive provides access to unique and difficult to recreate information, such as drill logs, assay results, and underground geologic maps, that is invaluable to land and resource management organizations and the minerals industry.
An effort to preserve the data began in 2009, and the entire collection of dockets was electronically scanned. The scanning process used optical character recognition (OCR) when possible, and files were converted into Portable Document Format (.pdf) files, which require Adobe Reader or similar software for viewing. In 2010, the scans were placed online (http://minerals.usgs.gov/dockets/) and are available to download free of charge.