Diamonds in Ureilites: The Never Ending Story

Diamond is the most illustrious of all minerals. Made of pure carbon atoms packed into a dense isometric structure, diamond is treasured as a gemstone for its brilliant (adamantine) luster and supreme hardness, and is in demand for many industrial applications because of these same properties. On Earth, most natural diamonds form deep (>160 km) under continental cratons, where high static pressures (>45 kilobars) stabilize diamond relative to graphite, which is the low-pressure polymorph of pure carbon. Such diamonds are only fortuitously brought to the surface, carried as xenoliths or xenocrysts in explosive volcanic pipes known as kimberlites. To geoscientists, diamonds provide invaluable records of the extreme conditions and otherwise inaccessible environments in which they formed. Diamonds can also probe exotic extraterrestrial environments. Nanometer-sized diamonds also occur as a rare component of the most primitive carbonaceous chondrite meteorites, rocks which preserve the original components of the Solar System.

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