The 4C's of Diamonds
The 4C's of diamonds were originally developed by Robert M. Shipley, founder of The Gemological Institute of America (GIA) in the 1940's. The diamond grading system was developed to create a consistent set of terms that defined clear standards for communicating about diamonds. The 4C's were further refined under the direction of Richard T. Liddicoat, and the later generations of GIA staff. The 4C's are Carat, Clarity, Color and Cut.
Carat is a unit of weight, rather than size. Rarity means larger diamonds of the same quality are worth more per carat.
The GIA clarity scale includes eleven diamond clarity grades. The scale narrows at the top because there are very few diamonds in the higher clarity grades. Clarity grades assess the number, size, relief, and position of inclusions and blemishes.
The GIA D-to-Z scale is the industry standard for color-grading diamonds. Each letter represents a range of color based on a diamond’s tone and saturation.
The less color, the higher the grade. Even the slightest hint can make a dramatic difference in value.
Cut (proportions, symmetry, and polish) is a measure of how a diamond’s facets interact with light.