Black Diamonds Born in Deep Space

Jan. 18, 2007 — A new analysis of the world's toughest diamonds suggests they may not only be the most ancient objects on Earth — they may also be visitors from deep space. It's even possible they are the unaltered chunks of a long dead, exploded star.

The evidence comes in the form of telltale traces of nitrogen and hydrogen in black "carbonado" diamonds, which don't match any terrestrial signature.

Instead, the molecules seem to reflect a mixture of gases seen in interstellar space, says Steve Haggarty of Florida International University. He and colleagues Jozsef Garai, Sandeep Rekhi and Mark Chance have published a paper on the matter in a recent issue of Astrophysical Journal.

"There is absolutely nothing to compare with these objects," Haggarty told Discovery News, adding that "600 metric tons of carbonado diamonds have been mined, stolen, bartered and adorned in the last century."

That's but a small fraction of the world diamond supply and it all comes from just two places: the Central African Republic and Brazil. Oddly enough, neither place has any of the expected geological signs of being a diamond-bearing region.

Interest in carbonados is more than academic.

These diamonds are particularly prized because they are just as hard as regular diamonds but far tougher under stress. That makes them extremely sought after for industrial drilling and cutting uses.

Finding out how carbonado diamonds were created would not only help geologists search for more, but help diamond makers figure out how to synthesize the useful gems, Haggarty explained.

The extraterrestrial trace elements found by Haggarty and his team fits some other suspicious signs in the minerals, says Haggarty. For one thing, carbonado diamonds are very porous — a strange thing indeed for a mineral thought to have formed under extreme pressures deep in the Earth.

What's more, the diamonds often have a glazed side which appears to be some sort of weathering, said Haggarty. No known Earth weather can do that to a diamond. So was it, perhaps, the hard radiation "weather" of interstellar space?

Another puzzle is those two locations. Take plate tectonic movement of the continents back in time, and the Central African Republic and Brazil are joined.

"It's exactly the same piece of real estate," said Haggarty. "Not a single carbonado has been found in a conventional diamond setting."

One possible explanation is that the carbonado diamonds are a chunk of a star that exploded long before the formation of the Sun. The chunk was floating through space and was caught up in the formation of Earth, and it's been here ever since.

"I think that is not an unreasonable idea," said geologist ancient mineral researcher Robert Hazen of the Carnegie Institution of Washington's Geophysical Laboratory in Washington, D.C. "They are perhaps the oldest thing you can hold in your hand."