The US Geological Survey does not employ gemologists – while there have been several within our ranks historically, they have been amateur gemologists who have pursued their interest on their own time. Nevertheless, gems DO come from the ground, and could reasonably be construed to be an ultimate product of geology. The following question is typical of the kind we receive about gems.
Q: Is there somewhere in California near Modesto that I can have a rock collection looked at? We are almost positive that we may have found some raw rubies! They have passed the scratch test and are very heavy and hexagonal shaped. 209-xxx-xxxx
A: We can't do gemology for you - the US Geological Survey is tightly constrained to work on only particular national objectives that Congress sets, including mineral resource assessments, volcano hazards, etc.
My recommendation to you is that you contact a local gemological society and ask for guidance. I would NOT recommend going to any jewelry store, as they only focus and specialize on the end products.
You might try:
http://www.americangemsociety.org/ ... but keep in mind that this is a trade association of retail jewelers, independent appraisers, suppliers, and selective industry members, and only incidentally will they have any component that might be of help to you.
You would probably do better with:
...or even better with a local society of educated amateurs, like the San Diego Mineral and Gem Society:
Finally, please keep in mind that there are beryls and other igneous minerals like garnet and eudialyte that can easily be mistaken for rubies by inexperienced people. A true ruby is a pink to blood-red (so-called “pigeon blood”) colored gemstone, a form of the mineral corundum (aluminum oxide). Ruby has a hardness of 9 on the Mohs scale, and is considered one of the four precious stones, along with sapphire, emerald, and diamonds. The red color in a ruby is caused mainly by the presence of the element chromium in the crystal lattice.