CGA Gemstone Treatments & Enhancements 2

Question 1

Tanzanite is almost universally heat-treated before sale. What color change does this treatment produce?

Accepted Answer

Brown to blue-violet

Answer

Purple to colorless

Answer

Green to blue-violet

Answer

Yellow to orange

Question 2

Traditional surface (lattice) diffusion treatment of sapphires is distinguished from beryllium diffusion primarily because it:

Accepted Answer

Affects only a thin surface layer

Answer

Penetrates the entire stone uniformly

Answer

Uses a different element but penetrates deeply

Answer

Does not alter color at all

Question 3

Laser drilling in diamonds is used by gem treaters primarily to:

Accepted Answer

Access and improve the appearance of dark inclusions

Answer

Inscribe identification numbers on the girdle

Answer

Create decorative faceting patterns

Answer

Increase the diamond's refractive index

Question 4

A classic diagnostic feature of lead-glass fracture-filled diamonds is an iridescent color seen in fractures, called:

Accepted Answer

Flash effect

Answer

Adularescence

Answer

Chatoyancy

Answer

Aventurescence

Question 5

Which specialized laboratory technique is the definitive method for detecting beryllium in diffusion-treated sapphires?

Accepted Answer

LA-ICP-MS (Laser Ablation Inductively Coupled Plasma Mass Spectrometry)

Answer

Infrared spectroscopy (FTIR)

Answer

Raman spectroscopy

Answer

Energy-dispersive X-ray fluorescence (EDXRF)

Question 6

When GIA issues a grading report for a clarity-enhanced diamond that has been laser drilled, how is the treatment disclosed?

Accepted Answer

The treatment is noted in the clarity treatment section of the report

Answer

GIA refuses to issue reports for laser-drilled diamonds

Answer

The diamond is graded identically to untreated stones with no notation

Answer

Only a verbal disclosure to the submitter is made

Question 7

Which of the following gemstone treatments is generally considered permanent, stable, and widely accepted without special disclosure requirements in the corundum trade?

Accepted Answer

Moderate heat treatment of sapphires

Answer

Fracture filling with lead glass

Answer

Low-temperature wax impregnation

Answer

Surface diffusion with titanium