What is a diamond?

Diamond is the only gem made of a single element: carbon. Diamond is typically about 99.95 percent carbon. The other 0.05 percent can include one or more trace elements, which are atoms that aren’t part of a diamond’s essential chemistry. Some of them can influence its color or shape. Formation conditions also help determine a mineral’s identity.

Diamond forms under high temperature and pressure conditions that exist only within a specific depth range beneath the earth’s surface.

The four C's

Most diamonds used in jewelry are nearly colorless with yellow or brown tints—most often light yellow. Diamonds come in many colors other than yellow and brown. Some of the most rare colors are red, purple, and green. With colored diamonds, more color usually means higher value, so the brightest, purest colors are the most desirable.

GIA grades color on a scale from D-Z.

Few things in nature are absolutely perfect. That’s as true of diamonds as anything else. Diamonds have internal features, called inclusions, and surface irregularities, called blemishes. Together, they’re called clarity characteristics. Clarity is the relative absence of inclusions and blemishes.

A well-cut diamond can make light perform in breathtaking ways, resulting in a magnificent display of three important diamond attributes: brilliancefire, and scintillation.

Brilliance is the combination of all the white light reflections from the surface and the inside of a diamond. It gives a polished diamond its brightness. Fire is the word for the flashes of color you see in a polished diamond. Scintillation describes the flashes of light you see when the diamond, the light, or the observer moves.


Diamond weights are stated in metric carats, abbreviated “cts.” One metric carat (abbreviated “ct.”) is one-fifth (0.200) of a gram—just over seven thousandths (0.007) of an ounce. One ounce contains almost 142 carats. The metric carat is divided into 100 points. A point (abbreviated “pt.”) is one hundredth of a carat. An easy way to remember this is to think of carats as dollars and points as pennies. They’re even written the same way: $1.34 means one dollar and 34 cents, and 1.34 cts. means one carat and 34 points.