How to Grade a Diamond. Often when first-time buyers shop for diamonds that have been set as jewelry, they simply take the dealer's word for the stone's quality and value. While you might not need to grade diamonds for the market, learning the aspects of diamond grading can help inform your investment decision. The 4C's criteria--color, cut, clarity and carat weight--can teach you about your preferences and how to secure the best stone for the money.
Grade Diamonds for Color and Clarity
Evaluate your first impression of a diamond's color and clarity. Note whether it caught your eye with flashes of light or sat "quietly" with limited brilliance.
Examine color further. Even "colorless" diamonds have black, gray or brown streaks or specks that may or may not be visible to the naked eye. Note where your diamond falls on a scale from D to Z, with D being the most perfectly colorless and Z having pale yellow shading. D is the preferred standard.
Examine fancy, or brightly colored, diamonds. These colors pick up where the colorless "Z"-graded stones left off, at pale yellow.
Grade clarity from "flawless" to "imperfect." Flawlessness equals a clean look to the eye, with clear, even color throughout the stone. Imperfections refer to occlusions, or tiny natural fissures that diminish brilliance.
Grade Diamonds for Cut and Carat Weight
Evaluate the cut and size, or carat weight, of a diamond. Note whether the size compelements the shape and faceting.
Evaluate the cut in relation to the stone's color and clarity. Note whether a shallow cut makes the stone appear transparent, which detracts from brilliance. Note whether clarity is sufficient to support the shape of the cut.
Gauge price per carat weight by the rarity of a diamond, generally determined by where it lands on the color scale, and by the percentage of flaws the stone contains.
Consider your impression of the diamond as a whole, that is, how color and clarity are informed by cut and carat weight to produce the overall effect.
When learning about diamond grading, try to view loose stones rather than jewelry. Looking at loose stones will allow you to see and compare overall brilliance versus transparency much more easily.
Know your limits. Casual grading by the untrained observer or buyer is worthwhile in establishing personal preferences, but only a professional diamond grader has the broad-based knowledge to determine a particular stone's market value.