CGA Gem Identification & Grading Techniques

Question 1

What property is most commonly used to distinguish diamonds from simulants?

Accepted Answer

Refractive index

Answer

Hardness

Answer

Luster

Answer

Color

Question 2

What is the primary scale used to measure gemstone hardness?

Accepted Answer

Mohs Scale

Answer

Brinell Scale

Answer

Vickers Scale

Answer

Rockwell Scale

Question 3

What tool is typically used to examine internal inclusions in gems?

Accepted Answer

10x Loupe

Answer

Spectrometer

Answer

Microscope

Answer

Polariscope

Question 4

Which gemstone is typically treated with heat to enhance its color?

Accepted Answer

Sapphire

Answer

Emerald

Answer

Ruby

Answer

Topaz

Question 5

What does 'cut' refer to in the 4Cs of diamond grading?

Accepted Answer

Proportions and finish

Answer

Shape

Answer

Symmetry

Answer

Brilliance

Question 6

Which term refers to a gemstone’s resistance to scratching?

Accepted Answer

Hardness

Answer

Toughness

Answer

Durability

Answer

Luster

Question 7

Which instrument is used to measure a gem’s refractive index?

Accepted Answer

Refractometer

Answer

Spectroscope

Answer

Polariscope

Answer

Loupe

Question 8

Which clarity characteristic can lower a diamond's value the most?

Accepted Answer

Dark inclusions under the table

Answer

Feathers

Answer

Pinpoints

Answer

Cavities

Question 9

What is pleochroism in gemology?

Accepted Answer

Color variation by viewing angle

Answer

Light dispersion

Answer

Color zoning

Answer

Color change under lighting