American Mineralogist Crystal Structure database. Comprehensive crystal structure database covering every structure published in "The American Mineralogist", "The Canadian Mineralogist" and the "European Journal of Mineralogy"
Athena Mineralogy. Searchable database of minerals, many with photographs of specimens.
The British Geological Survey Lexicon of Named Rock Units. Searchable database of information on British rock units.
The Commonground Database. Free database of rock and mineral data from the Colorado School of Mines. (limited access)
Cornell's Digital Earth. Hosted by Cornell University's Institute for the Study of the Continents, this site includes an interactive, digital map of the world that allows users to retrieve & analyze information from a compilation of geological data about the Earth's surface and interior.
Mineralogy Database. Site contains mineral data with information on all known mineral species with photos of some; browse the database by crystallography, chemical composition, physical and optical properties, New Dana classification, Strunz classification, & alphabetical listings.
Minerals Yearbook. This annual USGS publication cover three broad areas in mineral and materials industries: Metals and Minerals, and Area Studies - Both Domestic and International.