Ringwoodite
A high-pressure form of olivine with a spinel structure, found in the shock veins of meteorites.
Ringwoodite is a high-pressure polymorph of olivine, (Mg,Fe)₂SiO₄, with a spinel-type crystal structure. It was first found in nature in 1969 in the shocked L6 chondrite Tenham, which fell in Queensland, Australia, in 1879, and was named after the Australian geoscientist A. E. (Ted) Ringwood, who studied high-pressure transformations of mantle minerals. It is usually blue to purple in thin section.
In meteorites, ringwoodite forms in and next to shock veins and melt pockets, where olivine was briefly subjected to pressures of the order of 20 gigapascals during impacts. Its presence, with companions such as majorite and wadsleyite, helps constrain peak shock pressures and durations, and its grain sizes help estimate how large and long-lived the shock pulse was. Ringwoodite is common in heavily shocked L chondrites, which are linked to a major asteroid break-up about 470 million years ago, and occurs in some Martian meteorites.
On Earth, ringwoodite is thought to be a major mineral of the mantle transition zone, between about 520 and 660 kilometres deep. A natural terrestrial ringwoodite was found in 2014 as an inclusion in a Brazilian diamond, and it contained water.
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