Reddit mentions of Secrets of the Gem Trade: The Connoisseur's Guide to Precious Gemstones

You buy a book like this and learn https://www.amazon.com/Secrets-Gem-Trade-Connoisseurs-Gemstones/dp/0972822321/ref=sr_1_1?s=books&ie=UTF8&qid=1485439537&sr=1-1&keywords=gem+trade

We generally grade stones by #1 #2 #3 and terminated with #1 being gem quality - completely inclusion free/ no cloudiness / basically glass clear

The most advanced "valuation in personal property, in the gems and jewelry field" education that you can receive worldwide is through the American Society of Appraisers (You have an ASA up your way; Adrian Smith out of Scotland), www.appraisers.org. I can't remember whether or not they still have correspondence courses. The National Association of Jewelry Appraisers does have a correspondence course.

As far as education in antique and period jewelry- that's a tough one and you'll have to travel for that. The ASA offers some. You can also go to Jewelry Camp in NY, NY, offered every summer (http://www.jewelrycamp.org/).

Gemology basics can be learned with reading. Gem-A is GB's gemological course- which is top notch. If you're looking for reading, start with Richard Litticoat's book on gemology (Call the GIA bookstore for this) and Richards Wise's book (https://www.amazon.com/Secrets-Gem-Trade-Connoisseurs-Gemstones/dp/0972822321/ref=sr_1_1?ie=UTF8&qid=1500599511&sr=8-1&keywords=richard+wise+gems)

Also- join the forum on www.gemologyonline.com