A listing of state, U.S., provincial, and various international geological surveys and associations
www.lib.berkeley.edu/EART/surveys.html

Information from and about the U.S. Geological Survey:
geology.usgs.gov

The USGS photo library has thousands of images online:
libraryphoto.er.usgs.gov/

In particular, see "Minerals close-up" at
wrgis.wr.usgs.gov/docs/parks/rxmin/mineral.html

The USGS also has an online booklet, "Natural Gemstones":
pubs.usgs.gov/gip/gemstones/

The U.S. Naval Research Laboratory has put many crystal structures online at
cst-www.nrl.navy.mil/lattice

The Mineralogical Society of America’s "Higher Education Connection," with links to other sites dealing with minerals:
www.minsocam.org/

A site with extensive information about, and images of, a great variety of minerals is the Mineralogy Database:
webmineral.com

Links to images of rocks and minerals in the Smithsonian Institution Gem and Mineral Collection of the National Museum of Natural History is found at
www.nmnh.si.edu/minsci/images/gallery/gallery.htm

Pictures of microscope views of thin slices of igneous and metamorphic rocks, which often reveal interesting textural details, are online at
www.geolab.unc.edu/Petunia/IgMetAtlas/mainmenu.html

"The Mineral Gallery," a collection of images of and information about many minerals:
www.theimage.com/mineral/minerals1.html

A site of the University of Calgary provides links to many sites with information about mineral and rock properties and genesis:
http://www.geo.ucalgary.ca/~tmg/Research/thermo_links.html

A site featuring "Minerals and Gems on Stamps" from many countries, Afghanistan to Zimbabwe, is
stampmin.home.att.net/