CGA CGA Colored Gemstones & Pearl Evaluation

Question 1

Which color is considered the most valuable for a ruby?

Accepted Answer

Vivid red ('pigeon's blood')

Answer

Pinkish-red

Answer

Orangy-red

Answer

Dark brownish-red

Question 2

A gemologist wants to distinguish a natural sapphire from a synthetic sapphire. Which characteristic would be most useful?

Accepted Answer

Color zoning and natural inclusions

Answer

Refractive index

Answer

Specific gravity

Answer

Hardness

Question 3

What is 'pleochroism' in colored gemstones?

Accepted Answer

The ability to display different colors when viewed from different angles

Answer

The fluorescence of a gemstone under UV light

Answer

The dispersion of white light into spectral colors

Answer

The color saturation of a gemstone

Question 4

The 'big three' colored gemstones in the jewelry industry are:

Accepted Answer

Ruby, emerald, and sapphire

Answer

Emerald, sapphire, and tanzanite

Answer

Ruby, sapphire, and aquamarine

Answer

Emerald, amethyst, and sapphire

Question 5

What type of inclusion is most characteristic of natural Colombian emeralds?

Accepted Answer

'Jardin' (garden) of three-phase inclusions

Answer

Silk (rutile needles)

Answer

Fingerprint inclusions

Answer

Growth tubes

Question 6

For a CGA appraisal, what does 'treatment disclosure' mean for colored gemstones?

Accepted Answer

Informing the client of any enhancements that alter the gem's appearance or durability

Answer

Disclosing the gem's country of origin

Answer

Revealing the gem's natural color before cutting

Answer

Documenting the gem's refractive index in the appraisal report