I may, or may not, have mentioned at some point that I am a Gemologist. What on earth does that mean? Along with a lot of other things, I learned how to put a gem through a series of tests to determine its identity. Because I earned my degree at the Gemological Institute of America, I will be using their terms and descriptions. Other gem labs may use different terms.
The gem identification process separates gemstones by a combination of eliminating options through positive test results. A gemstone needs, at minimum, three positive results. Some require additional testing.
To begin, I describe the color: hue, tone, and saturation. Pigeon's blood red, cornflower blue, and grass green may evoke pretty pictures, but they fail to describe the characteristics if a color in a scientific manner. For that, I turn to a special color wheel and two scales.
The color wheel provides a range of hues to compare my gem to:
Tone describes how light or dark a gem is.
Saturation describes how strong or weak the hue is.
The color description of this stone color can be parsed two ways: Medium dark, moderately strong, slightly yellowish green (tone, saturation, hue). Or, slyG 6/4 (hue tone/saturation).
Next time: transparency.