Question 1: Parallax is caused by
  1. Double refraction
  2. A facet not being flat
  3. Lenses that need cleaning
  4. All the above
  5. 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
  1. – 0.005
  2. + 0.589
  3. Neither
  4. 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.
  1. True
  2. False
Question 4: A moderate-sized spinel inclusion in a spinel host gem will have a significant effect on its value.
  1. True
  2. False