Heh heh, no seriously, let's try that again.
Most insurance companies are now requiring that appraiser's have a gemologist degree. The two most well known schools are the GIA in New York and Califonia, and the FGA in London.
A gemological education will teach you how to know what stones are what, and how to judge quality. It's a diving platform from which springboard into the mad world of prices and markets, etc, etc, etc.
I believe experience to be one of the most valuable assets of a good appraiser. The more stones one has looked at, the more knowledgeable one is.
A good appraiser is one who is plugged into the market, lives and breathes it.