CGA Gemstone Treatments & Enhancements

Question 1

Which treatment is most commonly applied to rubies and sapphires to improve their color and transparency?

Accepted Answer

Heat treatment

Answer

Heat treatment is the most widely used enhancement for corundum gemstones, improving both color and clarity by dissolving rutile silk and altering trace element chemistry.

Question 2

Which organization publishes internationally recognized disclosure guidelines for gemstone treatments used by the trade?

Accepted Answer

CIBJO (World Jewellery Confederation)

Answer

CIBJO publishes the internationally recognized Blue Books, which establish gem grading nomenclature and disclosure standards for treatments accepted by the global jewellery trade.

Question 3

Fracture filling in diamonds to improve apparent clarity is most commonly accomplished using which substance?

Accepted Answer

High-lead-content glass

Answer

High-lead-content (lead) glass is injected into fractures to fill them; its refractive index close to diamond's makes the fractures nearly invisible, but the process is non-permanent.

Question 4

What does the acronym HPHT stand for in the context of diamond color treatment?

Accepted Answer

High Pressure High Temperature

Answer

HPHT (High Pressure High Temperature) treatment subjects diamonds to conditions that mimic the earth's mantle, permanently altering color by annealing structural defects responsible for undesirable tints.

Question 5

Beryllium diffusion treatment became a major trade concern in the early 2000s and is primarily associated with which gemstone?

Accepted Answer

Sapphire

Answer

Beryllium diffusion of sapphires was discovered around 2001–2002; the light element penetrates deep into the stone, producing dramatic orange, yellow, or padparadscha-like colors undetectable by standard gemological testing.

(CGA) Certified Gemologist Appraiser Practice Test

(CGA) Certified Gemologist Appraiser Practice Test

CGA Gemstone Treatments & Enhancements