CGA Colored Gemstones & Pearl Evaluation Flashcards
6 cards from real CGA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 CGA Colored Gemstones & Pearl Evaluation flashcards as text
In colored gemstone grading, what does 'saturation' refer to?
Answer: The intensity or purity of a gemstone's hue
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.
What is 'heat treatment' in the context of sapphires, and must it be disclosed?
Answer: A common enhancement that improves color and clarity; must always be disclosed
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.
Which gemstone variety is known as 'trapiche,' featuring a star-like pattern with six spokes?
Answer: Emerald, ruby, and sapphire can all occur as trapiche varieties
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.
What is the primary purpose of using a Chelsea filter when examining colored gemstones?
Answer: To help distinguish certain natural gemstones from their synthetic counterparts or common imitations
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).
For a CGA appraisal, what does 'country of origin' determination add to a colored gemstone's value?
Answer: Prestigious origins like Burmese ruby or Colombian emerald can significantly increase market value
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.
What is a 'doublet' in gemology, and why is it important for CGA appraisers to identify?
Answer: An assembled stone made of two layers; must be disclosed as it is not a single natural gem
A doublet is an assembled stone composed of two separate layers (often a natural gem crown bonded to a glass or synthetic pavilion) designed to simulate a more valuable gem, and must be identified and disclosed since it misrepresents the stone's nature.