GIA Diamond Grading and Identification 4

Question 1

Which instrument is primarily used to separate a natural diamond from a cubic zirconia based on thermal conductivity?

Accepted Answer

Diamond thermal tester (probe)

Answer

A diamond thermal tester measures thermal conductivity, which is exceptionally high in diamond compared to simulants like cubic zirconia.

Question 2

What is the refractive index of diamond?

Accepted Answer

2.417

Answer

Diamond has a refractive index of 2.417, one of the highest of any natural gemstone.

Question 3

A 'knot' inclusion is best described as:

Accepted Answer

A diamond crystal that reaches the surface of the finished stone

Answer

A knot is an included diamond crystal that extends to or breaks the surface of the polished stone.

Question 4

Which GIA cut grade is the highest achievable for a standard round brilliant diamond?

Accepted Answer

Excellent

Answer

GIA's highest cut grade is 'Excellent,' which represents the top tier of cut quality for standard round brilliant diamonds.

Question 5

In GIA terminology, what is the 'culet'?

Accepted Answer

The small facet or point at the very bottom of the diamond pavilion

Answer

The culet is the small flat facet (or pointed tip) at the very bottom of the pavilion.

(GIA) Certified Diamonds Gemological Institute of America Practice Test