CGC Crystal Structure & Mineralogy

Question 1

Which crystal system is characterized by three axes of equal length meeting at right angles?

Accepted Answer

Cubic (Isometric)

Answer

Hexagonal

Answer

Orthorhombic

Answer

Tetragonal

Question 2

On the Mohs hardness scale, which gemstone has a hardness of 9?

Accepted Answer

Corundum (Ruby/Sapphire)

Answer

Topaz

Answer

Diamond

Answer

Quartz

Question 3

What term describes the tendency of a mineral to break along flat planes related to its crystal structure?

Accepted Answer

Cleavage

Answer

Fracture

Answer

Parting

Answer

Tenacity

Question 4

Diamond belongs to which crystal system?

Accepted Answer

Cubic (Isometric)

Answer

Hexagonal

Answer

Tetragonal

Answer

Trigonal

Question 5

Which property describes the ratio of a gemstone's weight to the weight of an equal volume of water?

Accepted Answer

Specific Gravity

Answer

Refractive Index

Answer

Birefringence

Answer

Luster

Question 6

Emerald is a variety of which mineral species?

Accepted Answer

Beryl

Answer

Corundum

Answer

Tourmaline

Answer

Spinel

Question 7

What is the name for a crystal defect where a foreign atom replaces an atom in the crystal lattice, often causing color?

Accepted Answer

Isomorphous Substitution

Answer

Inclusion

Answer

Twinning

Answer

Polymorphism