CGA CGA Colored Gemstones & Pearl Evaluation 3

Question 1

In colored gemstone grading, what does 'saturation' refer to?

Accepted Answer

The intensity or purity of a gemstone's hue

Answer

Saturation describes the intensity or vividness of a gemstone's color, ranging from grayish or brownish (low saturation) to vivid or pure (high saturation), and is one of the key factors in color grading.

Question 2

What is 'heat treatment' in the context of sapphires, and must it be disclosed?

Accepted Answer

A common enhancement that improves color and clarity; must always be disclosed

Answer

Heat treatment is the most common enhancement for sapphires, used to improve color and dissolve silk inclusions; per industry ethics standards and CGA guidelines, all treatments including heating must be disclosed to the client.

Question 3

Which gemstone variety is known as 'trapiche,' featuring a star-like pattern with six spokes?

Accepted Answer

Emerald, ruby, and sapphire can all occur as trapiche varieties

Answer

Trapiche gemstones, most famously emeralds from Colombia but also rubies and sapphires, display a six-spoked wheel pattern caused by the inclusion of carbonaceous material or other impurities during crystal growth.

Question 4

What is the primary purpose of using a Chelsea filter when examining colored gemstones?

Accepted Answer

To help distinguish certain natural gemstones from their synthetic counterparts or common imitations

Answer

A Chelsea filter is a dichromatic loupe that transmits only deep red and yellow-green light, helping gemologists distinguish emeralds from their imitations (e.g., glass appears red while natural emerald may appear red too, but synthetic emerald appears bright red).

Question 5

For a CGA appraisal, what does 'country of origin' determination add to a colored gemstone's value?

Accepted Answer

Prestigious origins like Burmese ruby or Colombian emerald can significantly increase market value

Answer

For certain gemstones, prestigious geographic origins such as Mogok (Burma) rubies, Colombian emeralds, or Kashmir sapphires command substantial premiums in the market due to their historically exceptional quality and rarity.

(CGA) Certified Gemologist Appraiser Practice Test

(CGA) Certified Gemologist Appraiser Practice Test

CGA CGA Colored Gemstones & Pearl Evaluation 3