IGS Certification Exam: Sample Gemology Questions


Sample Gemology Questions - Brilliant Cut
What’s the difference between a brilliant cut and a step cut? Test your knowledge with these sample gemology questions from the International Gem Society certification exams. “1 carat brilliant cut diamond” by Mauro Cateb is licensed under CC By 2.0

The first step students will face in the International Gem Society (IGS) certification process is passing three 100-question written tests. All the questions are based on the materials in the IGS Learning Center.

What’s The Test Like?

The following sample gemology questions from the IGS certification exam should give you a sense of the scope of these tests. They’ll cover gemstone formation, properties of specific gems, gem identification, and testing, as well as faceting, grading, and appraising. If you’ve studied the material and think you’re ready, see how many you can answer correctly. Every answer has a brief explanation and/or links to the specific articles that cover the topic. If you’re interested in starting the self-study program or just curious about gemology, check out the questions and answers and see what it’s all about.

IGS Certification Exam: Ten Sample Gemology Questions

1. If you found a GGG in a diamond band, the GGG would be classed as:

  1. An imitation
  2. A homocreate
  3. Both
  4. Neither
Answer

C, Both. Any stone posing as something else is an imitation. GGG (gadolinium gallium garnet) is classed as a homocreate because it has no natural counterpart. See Synthetic Gemstones and Their Identification.

2. If an opal showed only blue color that was very bright, had a good cut, was only slightly directional, and had no imperfections on the top, it would be graded as:

  1. Below commercial value
  2. Commercial
  3. Good
  4. Fine
  5. Extra fine
Answer

C, Good. This stone has one factor in the commercial grade, one in the fine category, and two in the good category. See Appraising Opals.

3. Hydrothermal grown refers to:

  1. A natural process
  2. Laboratory grown gems
  3. Both

4. Brilliant faceting is determined by:

  1. Optical performance
  2. Triangular and kite shaped facets
  3. Dispersion
  4. All the above
  5. None of the above
Answer

B, Triangular and kite shaped facets. There are two basic styles of cutting: brilliant and step cutting. Step cutting features long, rectangular facets. Brilliant cutting uses triangular and kite shaped facets. While brilliant faceting usually enhances optical performance and dispersion, it is defined by the shape of the facets. Factories often do “brilliant style” cutting, with less than brilliant results. See Guide To Gem Cutting Terms.

5. HPHT treatments to improve color are done on which type of diamond:

  1. Type Ia
  2. Type Ib
  3. Type IIa
  4. Type IIb
Answer

C, Type IIa. See HPHT Diamond Update.

6. Demantoid is a species of garnet.

  1. True
  2. False
Answer

B, False. Demantoid is a variety of andradite. Andradite is a species of garnet. See Garnet Value, Price, and Jewelry Information.

Sample Gemology Questions - Demantoid
“Andradite,” demantoid variety, Antetezambato, Ambanja District, Diana Region, Antsiranana Province, Madagascar. © Rob Lavinsky, www.iRocks.com. Used with permission.

7. Hardness is a clear determination of how well a gem will wear.

  1. True
  2. False
Answer

B, False. You also need to take cleavage, brittleness, and light and chemical sensitivity into consideration. See The Physical Properties of Gemstones.

8. All mineral species have a different chemical composition.

  1. True
  2. False
Answer

B, False. Minerals are defined by a combination of their chemical makeup and their crystal structure. The classic example is diamond and graphite. Both have the same chemical composition, pure carbon, but their crystal structure makes them different. See How Gems Are Classified.

9. Cameos are made from both plastic and sea shells. They can be distinguished by:

  1. RI
  2. Hot point testing
  3. Optic sign
  4. Birefringence
  5. Specific gravity
Answer

B, Hot point testing. See Sea Shells and Destructive Tests: Hot Point.

10. Color change is defined as the difference between what is seen in incandescent and fluorescent light.

  1. True
  2. False
Answer

B, False. Many people use two electric lights to test for color change and they miss many examples! You must use natural light as no artificial light can match it. See Color Change Gems.

Ready to move on?

Complete sample quiz

Sample Gemology Questions - Cameo
“Cameo 1,” cameo etched into a shell, by Melinda is licensed under CC By 2.0