Gemology Certification Gem Treatments & Enhancements 3

Question 1

In the US colored gemstone trade, which organization's treatment disclosure guidelines are most widely followed?

Accepted Answer

AGTA (American Gem Trade Association)

Answer

The AGTA's treatment disclosure guidelines are the primary standard followed by US-based colored stone dealers and jewelers.

Question 2

An emerald graded as 'no oil' or 'no treatment' by a respected laboratory commands a significant price premium because:

Accepted Answer

High-quality untreated emeralds are extremely rare and highly valued by collectors

Answer

Because most fine emeralds are routinely oiled, high-quality stones with no treatment are exceptionally rare and can command multiples of the price of treated equivalents.

Question 3

Which type of surface coating applied to colorless topaz creates an iridescent 'mystic' or 'rainbow' effect?

Accepted Answer

Chemical vapor deposition (CVD) thin-film coating

Answer

Chemical vapor deposition deposits an ultra-thin metallic film on the pavilion of colorless topaz, creating the rainbow iridescence seen in 'Mystic Topaz.'

Question 4

In the diamond trade, a stone described as 'clarity enhanced' has most likely undergone which specific process?

Accepted Answer

Fracture filling to minimize white cracks or feathers

Answer

The term 'clarity enhanced' in the diamond trade specifically refers to fracture filling, where a glass-like substance is injected into feathers to make them less visible.

Question 5

Which treatment applied to blue sapphires involves introducing titanium and iron into a thin surface layer of the stone at high temperatures?

Accepted Answer

Surface (lattice) diffusion

Answer

Surface or lattice diffusion introduces color-causing elements like titanium and iron into the outer layer of colorless or pale corundum, producing blue color only skin-deep.

Gemology Certification Practice Test

Gemology Certification Practice Test

Gemology Certification Gem Treatments & Enhancements 3