Black Diamond Pendants

Treated Black Diamond Jewelry

There are several treatment techniques that are used to produce or enhance black diamonds. In 1904, Sir William Cookes, an English chemist and physicist, discovered that when a diamond was enveloped in radium salt, it changed color to a dark green. However, the process also rendered the diamond radioactive. In fact, a diamond so irradiated by Cookes was presented to the British Museum in 1914. There it rests today. Neither its color nor its radioactivity has faded. Therefore, this irradiation treatment is not employed.

A much safer form of irradiation to produce quality black diamonds was developed in the 1960s. Neutron bombardment – by way of the piles of a nuclear reactor – produces a dark green to black color that penetrates the entire stone. However, a cool down period is necessary. Because of this and a certain justifiable trepidation at the mention of radioactivity, few dealers offer irradiated black diamonds. In fact, the process is banned in the United States, although a number of stones do make it into the country. Accordingly, to be on the safe side, all black diamonds should be tested for residual radioactivity. The Yehuda Diamond Company, of New York, says that there is a simple test that can be performed. If you look through a small transparent area of the gem with a strong fiber optic light, the stone will have a green tint. Natural black diamonds, on the other hand, look completely black.

An alternative, and certainly safer, treatment than irradiation to produce gem quality black diamonds, is HPHT – High Pressure Heat Treatment. With temperatures ranging in the vicinity of 1260° F, the stone is held under pressure for a specified length of time. The situation is referred to as a reducing atmosphere – which means under conditions of little oxygen. This would approximate conditions at a certain depth under the earth’s surface. This is all according to the Toronto-based gemological laboratory, Harold Weinstein, Ltd.