Understanding Gemstone Color

Perhaps one of the most important factors when judging a gemstone is its color.  Interestingly, the way color of “colorless” or white diamonds and the color of colored gemstones is judged, is very different.  For diamonds, the stone is turned face down under a light source, and the body color is investigated.  Held this way, the diamond will not sparkle, but glow. 

Colored gemstones are evaluated face up, which is the way you would look at the stones when set in jewelry.  The refracted color is then judged.  This means that that a light beam is directed at the stone.  Some of this light is bounced back.  A well-cut stone will result in more light being refracted and thus creating a more beautiful color. 

A gemstone’s color is described in three ways:

• Hue:  This is essentially the type of color.  It is refers to the way color is used in general speech.  These are blue and green hues.  Greenish blue means that the main color is blue, with secondary green hues.  Orange-pink has equal amounts of orange and pink.  The much desired padparadscha stones are typically orangy pink, pinkish orange or orange-pink. 
•  Saturation:  This is the amount of color.  Paraiba stones which are typically a Caribbean sea blue are known for their high degree of saturation.
• Tone : This is how light or dark the stone is.  Too light and the stone can appear washed out, too dark and the stone appears dull. 

It turns out that saturation and tone work hand-in-hand to produce the most vivid hues.  Lighter tones are required for yellow, darker tones for blue and medium to darker tones for red and green.  Too much tone will result in the saturation of the gemstone actually declining.