Scientists find 'missing ingredient' for pink diamonds

More than 90 percent of all the pink diamonds ever found were discovered at the recently closed Argyle mine in the remote northwest of Australia.

But exactly why Argyle, which unlike most other diamond mines does not sit in the middle of a continent but on the edge of one, produced so many pink gems has remained a mystery.

In a new study published in the journal Nature Communications, a team of Australia-based researchers said the pink diamonds were brought to the Earth's surface by the breakup of the first supercontinent around 1.3 billion years ago.

Hugo Olierook, a researcher at Curtin University in the state of Western Australia and the study's lead author, told AFP that two of the three ingredients for forming pink diamonds had already been known.

The first ingredient is carbon and it must be in the bowels of Earth. Anything shallower than 150 kilometers deep would be graphite - "that stuff in your pencils, not nearly as pretty on an engagement ring," Olierook said.

The second ingredient is just the right amount of pressure, to damage the otherwise clear diamonds. "Push just a little bit and it turns pink. Push a little too hard and they turn brown," he said.

Most of the diamonds discovered at Argyle were of this less valuable brown hue, he added. The missing ingredient was the volcanic event that sent the diamonds shooting up to the Earth's surface, where humans could get their hands on them.