San Diego Natural History Museum
San Diego Natural History Museum: Mineral Matters: Hardness
Identifying a mineral by hardness? This website explains how to use the Mohs' hardness scale and provides examples.
James Madison University
James Madison University: Mineral Hardness and Cleavage
An explanation of the Mohs Hardness scale is followed by illustrations of crystal structures and cleavage.
Other
Rockmans Trading Post: Welcome to the Mineral Information Finder
During your lifetime, you will use more than a million pounds of rocks, minerals, and metals. Dig through this web site and find out how.