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“Spinel,” 0.87 cts., long emerald cut. © Dan Stairs Custom Gemstones. Used with permission.
If you’ve made it through our 3-part refractometer guide for gemologists, test your knowledge of refractive index (RI) analysis with this mini-quiz. Click on the link at the end of the quiz to see the correct answers. Got some wrong? Check out the refractometer review section below.
1. Parallax is caused by
- Double refraction
- A facet not being flat
- Lenses that need cleaning
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