Naturally black diamonds are extremely rare and can have a very high value, depending on the cut, color, clarity and carat size of the diamond. The most accurate way to learn the value of a black diamond is to have it appraised by a jewelry appraiser or a jeweler.
Though natural black diamonds are rare, many black diamonds exist in the marketplace. The majority of these are irradiated and heat treated to create an even color and increased durability, which makes the stone less valuable than one that naturally has an even black color. The black color in these diamonds is created by a great number of impurities or dark inclusion that are present in the stone. The more evenly these are distributed, the darker the stone, resulting in a greater value of the black diamond.