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

CIBJO

Answer

GIA

Answer

WJA

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

Untreated emeralds are more common than treated ones

Answer

Treatment increases emerald durability making untreated stones less practical

Answer

Untreated emeralds have measurably higher refractive indices

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

Electrostatic coating

Answer

Beryllium diffusion

Answer

Lead glass filling

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

Laser drilling to remove dark inclusions

Answer

HPHT to reduce color grade

Answer

Irradiation to improve brilliance

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

Beryllium diffusion

Answer

Standard heat treatment

Answer

Irradiation

Question 6

Why is disclosure of gemstone treatments ethically and legally required in professional gem trade transactions?

Accepted Answer

Treatments materially affect value, and buyers have the right to make informed purchasing decisions

Answer

Treatments always reduce gem durability significantly

Answer

Treated gems cannot be certified by laboratories

Answer

Disclosure is only required for stones above 1 carat

Question 7

Which characteristic of a fracture-filling treatment in an emerald makes it considered 'minor' versus 'significant' on a lab report?

Accepted Answer

The degree to which the filler affects the apparent clarity of the stone

Answer

The age of the filling material

Answer

The type of oil or resin used

Answer

Whether the filling was applied by the miner or the dealer