Eye of the beholder

The post the other day about the Gem of Tanzania brought up a topic worthy of a bit more attention. How is a fossil or mineral valued? There's not really an obvious answer. No handy flowchart to follow, no book to look up. There are gemological societies and institutions that will provide assessment and authentification services. For big ticket items, you might approach an auction house. You could look online and try to get an idea of market worth. Even take it in to a fossil shop. All possibilities, but none will give you a cast-iron figure because ultimately it's highly subjective.

Obviously, with some things it'll be a bit easier. Were someone to bring me a Green River fish, for example, I could give them a pretty good idea of retail value. A jeweller presented with a diamond cut in a standard fashion would be able to provide a solid assessment based on weight and clarity, etc. Bring in something slightly more unusual and things get a lot more tricky.

At the show in Tucson, I have bought stuff by the box in a marketplace on one side of the road, then crossed to a hotel where I've found one piece of exactly the same mineral, from the same locality, on sale for more than the entire box I've just bought. Clearly some people are simply more expensive than others, but there is a market for collector pieces - examples of exceptionally high standard - where prices can get scarily high. If there are enough people around that might want a piece then the potential value is raised. Supply and demand. That market isn't always accessible, but it's a factor that should influence any judgement. One man's rock is another man's gem.