The cut of the diamond is how well it is able to transmit light. Precise artistry and workmanship are required to fashion a stone so its proportions, symmetry, and polish deliver the magnificent return of light only possible in a diamond. The cut of the diamond is then evaluated based on brightness, fire or scattering of light into rainbows and scintillation which refers to the amount of sparkle the diamond produces. The cut is then ranked from "poor" to "excellent."
Clarity refers to the presence of imperfections in the ring which are referred to as "inclusions" or "blemishes" in or on the stone. The clarity of the diamond is based on the number, size, relief, nature and position of these characteristics, as well as the general appearance of the stone. The stone is then ranked from "included" to "flawless" using the GIA Diamond Clarity Scale. The closer that the diamond clarity is to "flawless," the more valuable it is.
The diamond color evaluation of most gem-quality diamonds is actually based on the absence of color. GIA's diamond D-to-Z color grading scale is the industry's most widely accepted grading system. The scale begins with the latter D, representing colorless, and continues with increasing presence of color the letter Z. Typically, the better the grade, the more expensive the stone.
Carat weight is how much a diamond weighs. A metric "carat" is defined as 200 milligrams. Diamond price typically increases with carat weight, because larger diamonds are more rare and valuable.