Advice for Determining Gemstone Value
Advice for Determining Gemstone Value

Professional Gemologist Certification Course

Advice for Determining Gemstone Value

Is it Worth It? Four Exercises

Of course, these exercises have limits. You can't always accurately judge gem colors through pictures on a computer monitor. Thus, when possible, I'll give you image comparisons to work with. Also, values vary over time, so I'll give you prices to use for each exercise. (Editor's note: the IGS Gem Price Guide numbers and information Donald Clark quotes are based on 2016 values).

Be sure to review the following articles:

You're looking for gems for your custom jewelry settings that will complement the quality and labor you've put into your settings. Of course, you want them at prices that will allow profit. While shopping at a local gem show, you find the following items: a tourmaline, a Thai ruby, an African ruby, and an emerald.

Tourmaline Gemstone Value

You come across this tourmaline with a distinctive personality. You don't find this in most elongated, green tourmalines.

For some time, you've had a special design in mind for a long, thin, emerald-cut gem. This custom-cut, eye-clean stone weighs 4.6 carats. The asking price is...


Donald Clark, CSM IMG

The late Donald Clark, CSM founded the International Gem Society in 1998. Donald started in the gem and jewelry industry in 1976. He received his formal gemology training from the Gemological Institute of America (GIA) and the American Society of Gemcutters (ASG). The letters “CSM” after his name stood for Certified Supreme Master Gemcutter, a designation of Wykoff’s ASG which has often been referred to as the doctorate of gem cutting. The American Society of Gemcutters only had 54 people reach this level. Along with dozens of articles for leading trade magazines, Donald authored the book “Modern Faceting, the Easy Way.”


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