About the International Gem Society (IGS)
…Come join our community! About the Founder Posing with some Quartz Donald Clark, CSM founded the International Gem Society in 1998. Donald…
2015 Clark Scholarship
Donald Clark, CSM, posing with some Quartz The International Gem Society (“IGS”) was founded by Donald Clark, CSM with the mission…
A Tribute to Bench Jewelers
…afraid I would swap it with a lower-quality stone. How many 5-ct, heart-shaped diamonds do you think I kept in stock? Donald Clark, CSM IMG Repair…
IGS Professional Gemologist Course
…provide an affordable education in gemology. IGS’s founder — Donald Clark, CSM IMG — created a robust testing process…
Feldspar Value, Price, and Jewelry Information
…(brown). Comments by Don Clark, CSM IMG Feldspars are our most common mineral, making up over 99% of the earth’s crust. Their formation…
How to Orient Sapphires with Silk Inclusions
…full of invisible inclusions that leave them a bit less than fully transparent. Donald Clark, CSM IMG Follow-Up Questions Thanks for the information.…
Refractive Index List of Common Household Liquids
…list was compiled from information provided by Donald Clark, CSM IMG, Dr. Gerald Wykoff, Dr. Clive Washington, Roy Kersey, and others. Vegetable…
A View of the Quartzsite Gem Shows
…gem shows listed at the end of Mr. Clark’s article for exact locations, dates, and times. By Donald Clark, CSM IMG 7 minute read These crystals…
Product Review: GL SpectroLite
…prove helpful should you locate one. By Donald Clark, CSM IMG 2 minute read The GL SpectroLite, shown here with a prism spectroscope, an LED light,…
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