Black Diamond Basics

Black diamonds get their color from inclusions, which often consist of graphite. These inclusions make black diamonds more prone to breakage than colorless diamonds. They are opaque--light can't pass through them--and difficult to cut.

Treatments

Most black diamonds on the market today come out of the ground a dark green and non-uniform color, so they undergo treatment to become a more uniform, black color. From a collector's perspective, treatments reduce the value of a gemstone. Treatments are often not disclosed to buyers. Sometimes your gem dealer doesn't know.

Carat Weight

Black diamonds are available in a variety of carat weights. Generally, the larger a stone is, the more it is worth. Large stones (of 2 or more carats) that have not been treated are incredibly rare.

The Other C's

Most people have heard about the four C's used in judging diamonds--cut, color, clarity and carat. Black diamonds are judged differently, especially when it comes to color and clarity because the color comes from inclusions that make the stone dark, and those are not desirable traits in the colorless-diamond market.

Value of Black Diamonds

Black diamonds are available at a variety of price points, but you can generally expect to spend between $100 and $400 per carat.

Source:

Gemological Institute of America

Rapaport diamond information

More Information:

Pricescope