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‘Super-deep’ diamond discovery brings unseen mineral to Earth’s surface

A diamond formed at greater depth than normal has been discovered, containing a rare example of an unstable mineral.
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A newly discovered diamond has an inclusion that adds to its value, according to a recent article from the University of Alberta. Found in South Africa’s Cullinan Mine, the gem contains calcium silicate perovskite, a mineral that has never been observed aboveground.

Despite being the world’s fourth most abundant mineral, this type of perovskite is found deep inside the Earth and is too unstable to be maintained above the planet’s crust under normal circumstances. However, the high durability of the diamond protected this example and allowed for closer examination by scientists.

The inclusion of this rare mineral occurred because the gem was formed much deeper than most diamonds—its kimberlite lay closer to 700 km (434 mi) below the surface than the typical depth of 150 to 200 km (93 to 124 mi).

Graham Pearson, the University of Alberta professor who found the diamond (along with a team of other researchers from universities in British Columbia, Italy, the U.K., and South Africa), says the discovery not only proves the mineral exists, but also gives scientists crucial information regarding what happens to oceanic crust within the Earth’s mantle.

This is not Pearson’s first scientifically significant diamond find. He also discovered a preserved example of the world’s fifth most abundant mineral, ringwoodite, in a diamond in 2014.

A study on the gem and its perovskite inclusion was published last week. For the University of Alberta’s coverage of the discovery, click here.

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