CS 8 Flashcards
What two coloring agents are usually responsible for color change in gemstones?
Chromium and vanadium
In practice, what GIA Colored Stone Grading tone levels apply to transparent colored stones?
Levels 2- 8, Only tone levels 2 through 8 are used for grading colored stones. See “Using GIA Terms to Describe Gemstone Color” in Colored Stones Assignment 8
Most defects in colored stone proportions are
compromises made by the cutter to produce economically viable gems.
Variations in conditions and coloring agents that occur during crystal growth can result in
color zoning
Generally, cool-colored stones with low saturation look
grayish
When a singly refractive stone shows a second color face-up, this is
because light reflected within the stone interacts with light transmitted through it.
Extinction results from
deep pavillions
Which abbreviation does the GIA Colored Stone Grading System use for a slightly purplish red hue?
slpR
Slightly purplish red is abbreviated as slpR. In GIA Colored Stone Grading System color abbreviations, the dominant hue is always capitalized. See “Using GIA Terms to Describe Gemstone Color” in Colored Stones Assignment 8.
The first impression of an object’s basic color is its
Hue
Before looking at the color of a gem, clean the stone, and then pick it up by its girdle with tweezers or place it on a background that is
neutral color
For consistency, you should view colored stones under what type of lighting whenever possible?
Daylight-equivalent fluorescent
Use trade terms that imply geographic origin only if the
gem’s actual source is known
The cutter’s main goal is to
produce a stone with the highest possible value.
In general, attractive colored stones tend to have highly saturated hues and
medium to medium-dark tone
Which gemstone occurs in almost every color?
Tourmaline
