CGC Study Guide 2026
Everything you need to pass the CGC exam in one place: the exam format, every topic to study, real practice questions with explanations, flashcards, and full-length practice tests. Free, no sign-up needed.
📚 CGC Topics to Study (21)
✍️ Sample CGC Questions & Answers
1. Which gemstone is most commonly used in custom engagement rings?
Diamonds are overwhelmingly the most commonly used gemstone in custom engagement rings due to their exceptional brilliance, durability (being the hardest known natural material), and symbolic association with everlasting love and commitment. Their timeless appeal and versatility in various settings make them a classic choice.
2. Which gemstone characteristic determines its clarity grade?
A gemstone's clarity grade is determined by the presence and visibility of internal features called inclusions, and external imperfections known as blemishes. The fewer and less noticeable these characteristics are under 10x magnification, the higher the clarity grade, as they can obstruct light and diminish the gem's brilliance.
3. When conducting a laboratory techniques & safety review in Certified Gemstone Consultant, which approach yields the BEST results?
Systematic analysis using established frameworks ensures comprehensive coverage of all potential risks and provides consistent, reliable results.
4. In Certified Gemstone Consultant, what role does employee training play in laboratory techniques & safety?
Training empowers all personnel to recognize hazards, follow proper procedures, and respond effectively, making it a cornerstone of any safety program.
5. What effect does a gemstone treatment disclosure have on its market value?
Disclosure of treatments generally decreases a gemstone's market value compared to a natural, untreated stone of equivalent appearance because untreated stones are rarer.
6. What is the most common treatment applied to blue sapphires to improve their color?
Heat treatment is the most common and widely accepted treatment for sapphires, used to improve color and clarity by dissolving rutile silk and enhancing hue.