Gemstone Refractometer Mini-Quiz

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