“Black” Diamonds

An exotic type of diamondmay have come to Earth from outer space, scientists say. Called carbonado or "black"diamonds, the mysterious stones are found in Brazil and the Central African Republic. They are unusual for being the color of charcoal and full of frothy bubbles.

The diamonds, which can weigh in at more than 3,600 carats, can also have a face that looks like meltedglass. Because of their odd appearance, the diamonds are unsuitable as gemstones. But they do have industrial applications and were used in the drill bits that helped dig the Panama Canal. Now a team led by Stephen Haggerty of Florida International University in Miamihas presented a new study suggesting that the odd stones were brought to Earth by asteroidbillions of years ago. The findings were published online in the journal Astrophysical Journal Letters on December 20. The scientists exposed polished pieces of carbonado to extremely intense infrared light. The test revealed the presence of many hydrogen-carbon bonds, indicating that the diamonds probably formed in a hydrogen-rich environment-such as that found in space.

The diamonds also showed strong similarities to tiny nanodiamonds, which are frequently found in meteorites. “They’re not lenticel,“Haggerty said, "but they're very similar." Astrophysicists, he added, have developed theories predicting that nanodiamonds form easily in the titanic stellar explosions called supernovas, which scatter debris through interstellar space. The deposits in the Central African Republic and Brazil, he said, probably come from the impact of a diamond-rich asteroid billions of years ago, when South America and Africa were joined.