The GIA Clarity Scale includes eleven clarity grades ranging from Flawless to I3. Because diamonds form under tremendous heat and pressure, it is extremely rare to find a diamond that lacks any internal and external characteristics. These characteristics are a by-product of its formation and help gemologists separate natural diamonds from synthetics and simulants, and identify individual stones.
The GIA Color Scale extends from D (colorless) to Z (light yellow or brown). Although many people think of gem quality diamonds as colorless, truly colorless diamonds are actually very rare. Most diamonds used in jewelry are nearly colorless with tints of yellow or brown.
Color grades are determined by comparing each diamond to a master set. Each letter grade represents a range of color and is a measure of how noticeable a color is.
Some diamonds can emit a visible light when exposed to ultraviolet radiation, but fluorescence is not a factor in determining color or clarity grades. However, a description of its strength and color is provided on GIA Reports as an additional identifying characteristic.
The GIA Cut Scale ranges from Excellent to Poor. GIA provides a cut quality grade for standard round brilliant diamonds that fall in the GIA D-to-Z color range.
A polished diamond’s beauty lies in its complex relationship with light: how light strikes the surface, how much enters the diamond, and how, and in what form light returns to your eye.
The result is a magnificent display of three attributes. Brightness, is the combination of all white light reflecting from the surface and interior of a diamond. Fire describes the “flares” of color emitted from a diamond. Scintillation describes the flashes of light you see when the diamond, the light, or the observer moves.
A polished diamond’s proportions affect its light performance, which in turn affects it’s beauty and overall appeal. Diamonds with fine proportions, symmetry, and polish optimize their interaction with light, and have increased brightness, fire, and scintillation.
One carat equals 200 milligrams in weight. For diamonds under one carat, each carat is divided into 100 points – similar to pennies in a dollar. 0.75 ct. = 75 points, 1/2 ct. = 50 points.
The 4C’s provide a way to objectively compare and evaluate diamonds, but numbers alone can’t describe a diamond’s mysterious and captivating beauty – for that, you’ll have to visit your local jeweler to see one for yourself.