How a gemologist identifies gems

How a gemologist identifies gems

w/ Bill Thielbahr, gemologist

This talk will provide the audience with a description of how gemologists identify and grade gemstones — both diamonds and colored stones. Methods and instruments used by small-scale, company and independent gemologists are described and demonstrated. The small piece of the earth’s electromagnetic spectrum, called “LIGHT,” is discussed, including how light rays interact with gemstones to produce COLOR, the most dominant gemstone property. Important chemical, physical, and optical properties of gemstones are described along with criteria for grading gemstones. Information is presented linking a faceted gemstone’s grade to its wholesale value. Discussions will include gemstone imitations and synthetics (lab-grown) and how they differ from natural stones. Advanced methods to evaluate gemstones, not available to most gemologists, will be reviewed. At the conclusion of this talk, the audience will have gained some understanding of how a gemologist answers the question: “What is it, and what is it worth?”

• This program is free for MOI members.
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