GIA Diamond Treatments and Synthetics 2

Question 1

Which spectroscopic feature is most diagnostic for identifying a CVD-grown synthetic diamond?

Accepted Answer

Si-V defect emission at 737 nm

Answer

CVD synthetics commonly show a silicon-vacancy (Si-V) defect center emitting at 737 nm due to silicon contamination from the reactor walls.

Question 2

A diamond shows graining that appears whitish and reflects light differently than the surrounding crystal. This most likely indicates:

Accepted Answer

High-pressure high-temperature (HPHT) treatment

Answer

HPHT treatment can produce or alter graining patterns, sometimes creating whitish graining visible under magnification as the crystal structure is stressed.

Question 3

What is the primary purpose of annealing a diamond after irradiation?

Accepted Answer

To convert green surface color to a stable body color

Answer

Annealing after irradiation converts the unstable green skin color into deeper, more stable colors such as yellow, orange, or brown throughout the stone.

Question 4

Which characteristic is shared by both HPHT-treated and natural Type IIa diamonds?

Accepted Answer

Absence or very low nitrogen content

Answer

Both natural Type IIa diamonds and HPHT-treated diamonds that have been decolorized exhibit very low or negligible nitrogen, which is why treatment is effective on Type IIa candidates.

Question 5

The 'flash effect' seen in fracture-filled diamonds under magnification appears as:

Accepted Answer

Alternating blue-purple and orange-yellow colors along the fracture

Answer

The flash effect — alternating blue-purple and orange-yellow iridescence — is caused by thin-film interference of the glass-like filler within the fracture.

(GIA) Certified Diamonds Gemological Institute of America Practice Test

(GIA) Certified Diamonds Gemological Institute of America Practice Test

GIA Diamond Treatments and Synthetics 2