CDG Gemology & Mineralogy Fundamentals

Question 1

What is the study of minerals called?

Accepted Answer

Mineralogy

Answer

Mineralogy is the scientific study of minerals, encompassing their chemical composition, crystal structure, physical properties, and geological occurrence. It is a fundamental branch of geology. While gemology is related, it is a specialized field focusing specifically on gemstones, their identification, and valuation for jewelry purposes.

Question 2

What defines a gemstone?

Accepted Answer

Minerals or rocks prized for beauty and rarity

Answer

A gemstone is defined as a mineral, rock, or organic material that is prized for its beauty, rarity, and durability, making it suitable for use in jewelry or ornamentation. While many gemstones are minerals, not all minerals are considered gemstones, and some gemstones, like pearls or amber, are organic. The key is their aesthetic appeal and scarcity.

Question 3

Which crystal system has three unequal axes all at right angles?

Accepted Answer

Orthorhombic

Answer

The orthorhombic crystal system is characterized by three crystallographic axes of unequal lengths that are all mutually perpendicular (intersect at 90-degree angles). This specific arrangement of axes distinguishes it from other crystal systems, such as cubic (three equal axes at right angles) or tetragonal (two equal axes, one unequal, all at right angles). Many common minerals, like topaz and olivine, crystallize in this system.

Question 4

What is the Mohs scale used to measure?

Accepted Answer

Hardness

Answer

The Mohs scale of mineral hardness is a qualitative ordinal scale that measures the scratch resistance of various minerals. It ranks minerals from 1 (softest, like talc) to 10 (hardest, like diamond) based on their ability to scratch or be scratched by other minerals. This scale is a crucial tool for mineral identification and determining a gemstone's durability.

Question 5

What property refers to how light bends inside a mineral?

Accepted Answer

Refraction

Answer

Refraction is the phenomenon where light bends as it passes from one medium into another, such as from air into a mineral. This bending occurs because light changes speed when entering a material with a different optical density. A mineral's refractive index, which quantifies this bending, is a key optical property used in gem identification and understanding a gemstone's brilliance.

(CDG) Certified Diamond Grader Practice Test

(CDG) Certified Diamond Grader Practice Test

CDG Gemology & Mineralogy Fundamentals