4C’s of Diamond Grading
Cut: The precision with which a diamond is cut is the most critical factor in releasing its "fire" and "brilliance." Since it is the only factor that humans can control, it may be the most important of the 4C's.
During the cutting process, fifty percent of rough diamond material is usually lost. The facets, or planes, of the diamond should be placed in exact geometric relation to each other, the culet or "point" should be in the exact center of the bottom of the diamond and the diamond needs to be well polished. This symmetry is crucial for light entering the diamond to be reflected back to the eye as "fire." If these geometric proportions are compromised, the beauty and brilliance of the diamond are sacrificed for size.
Clarity: Nature has identified each diamond by natural inclusions: crystals, feathers, lines, etc. These traits developed in the diamond during its formation. Diamond clarity is determined by the absence of these inclusions—the fewer the inclusions, the more rare the diamond and the greater the value. Flawless and internally flawless diamonds are exceedingly rare. The term "flawless" is a highly restricted one. Under Federal Trade Commission rules a diamond can only be deemed flawless when no internal or external imperfections are visible to a professional eye under 10-power magnification using a binocular microscope in good light. While inclusions may not affect the beauty of a diamond, they do affect its value and price.
Color: Although most gem-quality diamonds when seen alone appear to be colorless to the untrained eye, there are subtle differences in shade. Fancy color in diamonds results from traces of other elements mixed with carbon during the diamond's formation. Diamonds with no traces of body color are extremely rare.
To determine a diamond's true color, the diamond is viewed from the side under balanced white light. It is compared to diamonds in a "Master Set" whose colors have been predetermined by the Gemological Institute of America (GIA).
Carat: The aspect of carat weight is the easiest to understand and refers to the size of the diamond. A carat weighs .2 grams and is subdivided into 100 points. A one (1) carat diamond therefore weighs 100 points and a half (½) carat diamond weighs fifty points or .50 carat. Due to the rarity of diamonds the value of the stone rises exponentially with an increase in carat weight. All gems are weighed in carats although each type of stone has a different weight, meaning a one-carat opal will not be the same size as a one-carat diamond.
4C’s of Diamond Grading