Category: Geology

A rare violet diamond, the largest of its kind ever found at Australia’s remote Argyle mine, will be the centrepiece of Rio Tinto’s annual pink diamonds showcase, the company said Tuesday.

The rough gem, discovered in August 2015 at a mine where more than 90 percent of the world’s pink and red jewels are produced, originally weighed 9.17 carats and had etchings, pits and crevices.

After weeks of assessment, the Argyle Violet was polished down to a 2.83 carat, oval-shaped diamond.

“Impossibly rare and limited by nature, the Argyle Violet will be highly sought after for its beauty, size and provenance,” Rio Tinto Diamonds general manager of sales, Patrick Coppens, said in a statement.

Rio Tinto did not put a figure on its worth, but said it had been assessed by the Gemological Institute of America as a notable diamond with the colour grade of Fancy Deep Greyish Bluish Violet.

It is not known how diamonds acquire their coloured tinge but it is thought to come from a molecular structure distortion as the jewel forms in the earth’s crust or makes its way to the surface.

Diamonds for sale as part of the annual Argyle pink diamonds tender can fetch US$1-2 million a carat. As a basic rule of thumb, pink and red diamonds are worth about 50 times more than white diamonds.

Rio Tinto said violet diamonds were extremely rare with only 12 carats of polished stone produced for the tender in 32 years.

“This stunning violet diamond will capture the imagination of the world’s leading collectors and connoisseurs,” Argyle pink diamonds manager Josephine Johnson said.

The 2016 tender will begin private trade viewings in June and travel to Copenhagen, Hong Kong and New York, Rio Tinto said.

Source: ‘Impossibly rare’ violet diamond found in Australia

The last of a group of dense minerals that make up much of Earth’s crust and upper mantle has been found tucked inside a meteorite that slammed into Australia 135 years ago. The newly discovered mineral, a variety of majorite, is potentially abundant in sinking tectonic plates and could help illuminate the behavior of the deep Earth, its discoverers say.

Each identical component of this mineral contains 32 magnesium atoms, 32 silicon atoms and 96 oxygen atoms arranged in a distorted cube. Natural samples of MgSiO3 tetragonal garnet, the mineral’s scientific moniker, had eluded scientists since the mineral was first artificially produced in 1985.

Naotaka Tomioka, a mineralogist at the Kochi Institute for Core Sample Research in Japan, and colleagues discovered 0.5-micrometer-wide grains of the mineral in a slice of the 19th century meteorite. While many minerals found in meteorites form when slamming into Earth, the new mineral formed in space when two asteroids collided at a relative speed of about 2 kilometers per second, the researchers report online March 25 in Science Advances.

One challenge remains for the researchers: As discoverers of the mineral, they now get to name it.

Source: One of Earth’s missing minerals found locked inside meteorite | Science News

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