Much more recently (tens to hundreds of million years ago), the would have been pushed to the surface in volcanic eruptions and deposited in igneous rocks known as kimberlites (blue-tinged in color and coarse grained) and lamproites (rich in potassium and also from deep in the mantle.) They are made from carbon-containing fluids that dissolve minerals and replace them with what over time become diamonds. Those super-deep Earth diamonds form in a cauldron up to 1,000 degrees F and at 240,000 times the atmospheric pressure at sea level.
(And some come from space, as described in this article below and in a just published Nature Communications 3 article about diamonds in the Almahata Sitta meteorite that crashed in Sudan in 2006.) They are generally formed at depths of 100 to 150 miles in the Earth’s mantle, although a few have come from as deep as 500 to 600 miles down. That paper was authored by University of Nevada, Las Vegas geoscientist Oliver Tschauner and colleagues, and appeared in the journal Science 2.ĭiamonds are a solid form of carbon with a distinctive cubic crystal structure. In addition to being a first, the ICE- VII discovery adds to the growing confidence of scientists that much H 2O remains deep underground, with some inferring as much deep subsurface water as found in the surface oceans. While samples of H 2O ice have been identified in diamonds before, none were ICE- VII which is formed only under tremendous deep-Earth pressure. The additional discovery was of a tiny bit of water ice known as ICE- VII inside several other deep diamonds. But more important, it moves forward our understanding of what happens far below the Earth’s surface. Mineral science does not allow a specimen to be named until it has actually been found in name, and now this very common form of mineral finally will get a name. As reported in the journal Nature 1, the mineral is a variant of calcium silicate (CaSiO 3), created at a high pressure that gives it a uniquely deep-earth crystal structure called “perovskite,” which is the name of a mineral, too. And this field has in recent weeks gotten some important discoveries based on those diamond inclusions.įirst is the identification by Fabrizio Nestola of the Department of Geosciences at the University of Padua and colleagues of a mineral that has been theorized to be the fourth most common on Earth, yet had never been found in nature or successfully synthesized in a laboratory.
The strange and remarkable subterranean world where the diamonds are formed has, of course, never been visited, but has been intensively studied using a variety of indirect measurements.
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