Roles, Rules, and Rolls has a really great Matrix of Precious Stones — complete with pictures! I don’t know about y’all, but my treasure hordes tend to be disproportionately filled with a half dozen or so “common suspects” of questionable interest. I’d much rather have the scepter of the mummy king topped with a fluted facet of snake skin jasper rather than generic emerald #191.
Roger’s post is also a great example of how you can find all kinds of gaming resources by just scrounging through your every day life (often with little or no effort required to alter it).
I actually bought a large coffee table book and a smaller reference guide to germ stones to see what they look like and give better descriptions. Semi-precious stones are cheap in a place like New Mexico, and you can get a nice collection with samples bigger in size than this table. Gygax DMG has the best random gem generation table and their reputed magical properties (also listed in greater detail in both of my books about gems).
I was thinking of getting a gem collection, Emeralds, etc. You can make an adventure out of this – travel to Brazil and Thailand to look for and get better deals on the stones close to the source, one for each color of the rainbow! But ultimately give up on it.
Gem stones are NOT an investment, it is a scam, an expensive toy that only depreciates with each succeeding re-sale, much like a car. There is a subjective and esoteric six point appraisal system, that guarantees the dealer’s advantage, stones can deteriorate and some even DRY OUT over the years (like a “mere” Fire Opal that costs between five and ten grand!), and there are a lot of tricks that can be done to the stone (including “cooking” them, literally) to improve the stone’s appearance and reduce its value. I might have a Crow’s passion for everything shiny, but not enough money and too much caution to throw the money in the wind.