Gemstone Refractometer Mini-Quiz

Test your knowledge of refractometer gem analysis with this mini-quiz. You can review material on any question you miss at the end of the quiz.

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By Donald Clark, CSM IMG

Question 1

Parallax is caused by:

A. Double refraction

B. A facet not being flat

C. Lenses that need cleaning

D. All the above

E. None of the above

Question 2

If you use a red filter with your refractometer, you need to make an adjustment to your reading of

A. – 0.005

B. + 0.589

C. Neither

D. Both

Question 3

If you’re testing a gem and measured a high RI of 1.612 and a low RI of 1.608, the stone’s birefringence is 0.004.

A. True

B. False

Question 4

A moderate-sized spinel inclusion in a spinel host gem will have a significant effect on its value.

A. True

B. False

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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