The jewelry industry's insatiable appetite for variety is finally beginning to pay off big time for black diamond, a category of colored diamond that was once held in such low esteem among specialists in these gems that few carried it. But designers began showing collections of black diamond jewelry, willing to cross the color line and take a chance on stones that one New York dealer condescendingly described as "faceted lumps of coal." Consumers responded and black diamond today is a jewelry industry staple.
So why did so many in the trade regard black diamond as a lower-order form of carbon that didn't quite make the transformation to pure crystal diamond deep in the earth millions of years ago? Well, the judgment is harsh but correct. In India, where nearly all the world's faceted black diamonds are cut, they are known as "carbons," a shortening of "carbonado," a trade term for a specific variety of highly opaque and included industrial stone thought to be the toughest diamond known. While many black diamonds are not carbonados, all can be put under the large heading of industrial diamond known as "bort," a term derived from an old French word for bastard. This fact doesn't help matters any for what are best viewed as crystallographically-challenged diamonds.
According to gemologist Stephen Hofer, author of the landmark Collecting and Classifying Coloured Diamonds, most black diamonds are in "a transitional carbon state between graphite and pure diamond." This means most are polycrystalline aggregates as opposed to single crystals. "The typical black diamond," Hofer continues, "is composed of a mishmash of atoms rather than a regular, homogenous arrangement. As a consequence, their atomic lattice has many areas of weakness that cause stones to chip frequently on the wheel."
Cutting black diamonds is a time-consuming process, which is why most hail from India where low labor rates permit the man hours needed to fashion these stones. Essentially, says dealer Aaron Kavakeb of Gem Melody in New York, "You are cutting a giant black pique with diamond inclusions in it." For this reason, many black diamonds are marred by pits, breaks, and areas of transparency, even when pampered on the wheel.
To avoid the appearance problems common with natural-color black diamonds, some designers use easily-cut conventional stones with low color and clarity ratings that have been irradiated to make them look like black onyx: the ideal for black diamond.
Occasionally, a pure-crystal natural black diamond comes along that puts competing species to shame and is one of nature's glories. Such stones are ultra-rare and have been the object of a secret search among collectors that rivals the more public quest for fugitive colors such as red.
As Hofer demonstrates in his indispensable book, there has been a centuries-long hunt for a rarity called the "pure crystal black diamond." For instance, the 1839 catalog of Henry Philip Hope, whose giant blue diamond now in the Smithsonian is arguably the world's most famous diamond, lists a 1.25 carat black round-brilliant. The 1874 catalog of the Duke of Brunswick, Hope's best-known peer among 19th century collectors of colored diamonds, lists five blacks of varying shades from "noir transparent" to "macadam" (asphalt).