Russ from Rings & Things was kind enough to leave a comment (yay, someone actually reads this crazy thing!) about the gemstone index available on the Rings & Things website.
It's very important (and also kinda difficult) to be as informed and knowledgeable as possible about the various kinds of stones on the market when you are a jewelry designer. Not only do you want to be able to accurately identify your materials when talking to customers, but you also need be able to accurately judge quality and pricing when shopping for your materials.
Case in point: turquoise. I can't tell you how much fake turquoise I see at gemshows that is priced and marked as the genuine stone. In fact, there's so much fake stuff that there are even gradations of "fake" (turquoise dust mixed with binders, chalk/resin dyed to a turquoise color, howlite dyed to a turquoise color, plastic, etc.) Although, I suppose an argument could technically be made that beads made from turquoise dust ARE "genuine turquoise," but I would personally disagree with that.
While you're checking out the index, be sure to do some shopping as well. R&T is a great vendor!