New Mineral Discovered In Deep-Earth Diamond

fahrbot-bot shares a report from Scientific American: A diamond that formed deep in the earth's mantle contains a mineral never seen before in nature. The discovery is a rare glimpse into the deep mantle and may help reveal new information about the structure of the planet at depths of more than 660 kilometers. This, in turn, can help geologists better understand how the mantle controls the earth's plate tectonics. The mineral, calcium silicate perovskite, only forms under the incredibly high pressures that occur deep in the earth. The newly identified sample likely formed between 660 and 900 km below the planet's surface, says mineralogist Oliver Tschauner of the University of Nevada, Las Vegas. Though the mineral had previously been synthesized in the laboratory using 20 gigapascals of pressure (almost 200,000 times atmospheric pressure), it had immediately reverted to a different form when it was removed from that artificial high-pressure environment. So researchers had assumed it would be impossible to retrieve naturally occurring calcium silicate perovskite from the mantle. "The chances, we thought, of finding it were so low that we never really actively looked for it," Tschauner says. So it was a surprise when he and his colleagues, analyzing imperfections in a diamond from Orapa, Botswana, found three minuscule specks of calcium silicate perovskite. Calcium silicate is found in other forms, including wollastonite in the crust and breyite in the middle and lower regions of the mantle. But this version had a telltale cubic crystal structure that marked it as different from those versions of the mineral. Tschauner and his colleagues named the new mineral "davemaoite," after geologist Ho-Kwang "Dave" Mao, who carried out some of the pioneering experiments in using diamonds as presses to experimentally generate mantlelike pressures on the earth's surface. They announced the discovery on Thursday in Science.

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