CGC Crystal Structure & Mineralogy 2

Question 1

Which crystal system does quartz belong to?

Accepted Answer

Trigonal

Answer

Cubic

Answer

Orthorhombic

Answer

Monoclinic

Question 2

What term describes two distinct minerals that have the same chemical composition but different crystal structures?

Accepted Answer

Polymorphs

Answer

Isomorphs

Answer

Allotropes

Answer

Pseudomorphs

Question 3

Which type of luster is described as resembling the surface of a pearl or the inside of a shell?

Accepted Answer

Pearly

Answer

Vitreous

Answer

Adamantine

Answer

Silky

Question 4

Alexandrite is a variety of which mineral known for its dramatic color-change property?

Accepted Answer

Chrysoberyl

Answer

Spinel

Answer

Tourmaline

Answer

Garnet

Question 5

What is the cleavage quality of diamond described as?

Accepted Answer

Perfect in four directions (octahedral)

Answer

Poor in one direction

Answer

Imperfect in two directions

Answer

None

Question 6

The mineral group that includes jadeite and spodumene belongs to which family?

Accepted Answer

Pyroxenes

Answer

Amphiboles

Answer

Feldspars

Answer

Garnets

Question 7

Which optical phenomenon causes the star effect (asterism) seen in star rubies and star sapphires?

Accepted Answer

Reflection from needle-like rutile inclusions oriented along crystal axes

Answer

Dispersion of light by the crystal lattice

Answer

Interference from twinning planes

Answer

Diffraction from surface etch pits