Gemology Certification Gemology Gem Identification Techniques 5

Question 1

Which of the following best describes the difference between a doublet and a triplet in composite stones?

Accepted Answer

Doublets have two layers; triplets have three layers including a colored cement layer

Answer

A doublet is two layers cemented together, while a triplet adds a third layer—often a colored adhesive—to enhance color or add a protective crown.

Question 2

A gemologist observes curved striae and gas bubbles inside a red stone. This most strongly suggests:

Accepted Answer

Synthetic flame-fusion ruby (Verneuil process)

Answer

Curved growth lines (striae) and spherical gas bubbles are classic diagnostic features of Verneuil (flame-fusion) synthetic corundum.

Question 3

What does the term 'critical angle' mean in the context of gemstone identification?

Accepted Answer

The minimum angle of incidence at which total internal reflection occurs

Answer

The critical angle is the angle of incidence beyond which light undergoes total internal reflection rather than passing through the gem's surface.

Question 4

A stone tests positive on a diamond thermal probe but negative on a moissanite tester. Which conclusion is most appropriate?

Accepted Answer

The stone could be diamond or moissanite; additional testing is needed

Answer

Moissanite has thermal conductivity similar to diamond and can fool basic thermal probes; a dedicated moissanite tester is needed for differentiation.

Question 5

Hydrothermal synthetic emeralds can often be distinguished from natural emeralds by the presence of:

Accepted Answer

Chevron or nail-head spicule inclusions

Answer

Hydrothermal synthetic emeralds (like Gilson or Biron) often contain distinctive chevron or nail-head spicule growth patterns not seen in natural stones.

Gemology Certification Practice Test

Gemology Certification Practice Test

Gemology Certification Gemology Gem Identification Techniques 5