Gemology Certification Gemology Mineralogy & Gem Formation 2

Question 1

Which crystal system is characterized by three axes of unequal length, all meeting at right angles?

Accepted Answer

Orthorhombic

Answer

The orthorhombic system has three mutually perpendicular axes (a, b, c) all at 90° but all of different lengths.

Question 2

Pegmatite deposits are significant in gemology primarily because they:

Accepted Answer

Allow slow crystallization that produces exceptionally large crystals

Answer

Pegmatites cool and crystallize slowly from volatile-rich magmatic fluids, enabling growth of unusually large gem crystals such as tourmaline and beryl.

Question 3

The term 'specific gravity' in gemology refers to:

Accepted Answer

The ratio of a gem's density to the density of water at 4°C

Answer

Specific gravity (SG) is a dimensionless ratio comparing the gem's density to that of pure water at 4°C.

Question 4

Which metamorphic process is most responsible for the formation of gem-quality garnets?

Accepted Answer

Regional metamorphism at high pressure and temperature

Answer

Regional metamorphism subjects rocks to the high pressures and temperatures needed to stabilize the dense garnet crystal structure.

Question 5

A mineral's 'cleavage' is determined by:

Accepted Answer

Planes of weakness parallel to atomic bonding directions

Answer

Cleavage follows planes where atomic bonds are weakest, causing the mineral to break smoothly along those directions.

Gemology Certification Practice Test

Gemology Certification Practice Test

Gemology Certification Gemology Mineralogy & Gem Formation 2