There are a number of great sites with photos and charts and information on minerals and rocks.

Or – you could do a search for the mineral or rock in question!

Here are a couple of links to pages of specific focus.  Enjoy!

Chemical Data
Optical Mineralogy
Mineral Databases
Mineral Resources

Igneous Rocks - photos – from geology.com

Sedimentary Rocks - photos – from geology.com

Metamorphic Rocks - photos – from geology.com

And - geology.com

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