Rock & Gem

Love inside this Diamond!


While most diamonds are paired with deep looks of love, one diamond discovered in Botswana has delivered a deep look into planet Earth. To the average eye, the little black specks contained within this green octahedral diamond are nothing more than undesirabl­e inclusions and flaws. But to Cal Tech mineralogi­st, George Rossman, who purchased the diamond in 1987, they represent an exciting discovery— a new mineral dubbed davemaoite. This find provides a hint of the mineralogi­cal environmen­t of deep Earth.

Davemaoite (named for Ho-kwang “Dave” Mao, who has made pioneering discoverie­s in high-pressure mineralogy) formed at high temperatur­e and high pressure deep below Earth’s surface. Previously, it had only been produced in the lab, but according to a team led by geochemist, Oliver Tschauner, of the University of Nevada, Las Vegas, this marks the first time a specimen has been found in nature. Davemaoite offers “a rare glimpse of something that normally cannot exist on Earth’s surface,” per a recent report by publishers of the journal Nature. It provides rare clues about heat flow deep in the lower mantle of Earth in a region between the planet’s crust and core where direct sampling is inaccessib­le.

Per Tschauner, these little black specks survived a journey to Earth’s surface because of “the strength of the diamond that keeps the inclusions at high pressure.” Such deep-Earth diamonds are now viewed as important portals to give us vital clues as to the geology, geochemist­ry and geophysics deep down beneath our feet.

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