- As published by the magazine 'PNAS', they emerged after the collision of a large asteroid about 4,500 million years ago.

Additional examples of graphite with embedded diamond clusters. / PNAS

What is lonsdaleite? Science finds new explanations for these rare diamonds

Lonsdaleite is a rare hexagonal diamond shape that would have formed after an ancient dwarf planet in the solar system collided with a large asteroid about 4.5 billion years ago, according to a study published Tuesday by PNAS.

A team led by the Melbourne University of Technology (RMIT) claims to have confirmed, in ureilite meteorites from the dwarf planet's mantle, the existence of lonsdaleite, a mineral named in honor of British crystallographer Dame Kathleen Lonsdale.

"This study categorically demonstrates that lonsdaleite exists in nature," said McCulloch of RMIT and one of the study's co-signers.

In addition, he noted that the team had predicted that the hexagonal structure of lonsdaleite's atoms made it potentially harder than normal diamonds, which have a cubic structure.

The largest lonsdaleite crystals known to date are down to a micron in size, much finer than a human hair, and their unusual structure could help advance new techniques for fabricating ultrahard materials to make tiny pieces of machinery.

The team used advanced electron microscopy techniques to capture solid, intact slices of the meteorites and create snapshots of how lonsdaleite and regular diamonds formed.

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