Why Are Black Diamonds the Most Rare?

Myths and Lore

• Several cultures have had myths surrounding the black diamond, due perhaps to its unusual nature and rarity. Indian culture associated the stone with snake and spider eyes and with Yama, the Hindu god of death. The belief was that coming across the stone was a sign of impending death. Italian lore, on the other hand, viewed the stone as beneficial. A marriage in trouble could be saved if husband and wife both touched the stone.

History

• Black diamonds are also called carbonados ("carbonated"), a term coined by the Portuguese who thought the black diamonds resembled coal. The black diamond is so hard that Brazilians used it to polish Brazilian hardwood before shipping it to America, and it was later used to drill rocks for the Panama Canal. Black diamonds are more difficult to set because they are so hard. It can take a twenty-ton hydraulic press to break one, and the best substance to use in cutting a black diamond is another black diamond.

Differences from Conventional Diamonds

• Black diamonds have the hardness they do because of their structure. Conventional diamonds have a single-crystal structure, but black diamonds are made of millions of crystals stuck together. Conventional diamonds are also created by pressure deep underground, an unlikely origin for black diamonds because their porous nature means they were created in an environment where gases were easily trapped within the rock. Dated at between 2.6 and 3.8 billion years old, black diamonds are also older than conventional diamonds.

Geography

• No black diamonds have ever been found outside Brazil and the Central African Republic, not even in traditional diamond fields. And though they are separated by an ocean, diamonds from both countries have similar isotopes, indicating they have similar origins. Brazil and Africa are thought to have once been part of the same land mass, so it is not far-fetched to assume that originally, black diamonds existed in only one place on the planet. The question of how they were formed, however, was a mystery for a long time.

Origin

• Because of the differences between black diamonds and conventional diamonds, it is a common theory that black diamonds did not originate from within the earth. In 2007, scientists concluded that the diamonds were probably brought to earth in an asteroid long ago. This explains the age of black diamonds, as they would have formed long before arriving on earth. Scientists have also used radiation to identify hydrogen in black diamonds, an element common in interstellar space. Given this extraterrestrial origin, it is possible that no black diamonds will be found elsewhere in the world, making them perhaps more rare and desirable than ever.