Coorara meteorite, Rawlinna, Kalgoorlie-Boulder Shire, Western Australia, Australiai

Regional Level Types
Coorara meteorite	Meteorite Fall Location
Rawlinna	Town
Kalgoorlie-Boulder Shire	Shire
Western Australia	State
Australia	Country

Stone, Ordinary Chondrite, L6. Found 1966.
A total of 9 stones weighing 116.7 grams were recovered from the Nullarbor Plain. This highly shocked (S6) stone has two high pressure minerals, majorite and ringwoodite, contained in the shock veins.

Named after Coorara Station it was found on. Majorite was first found as a species in veinlets in the meteorite. It is a dark purple garnet, derived mostly from the original pyroxene, formed during high pressure shock events. It is distingushed from other garnets by having Si in octahedral as well as tetrahedral co-ordination. It regularly appears on lists of the top ten rarest gemstones in the world. However, before you race out to spend thousands of dollars buying one, it could be worthwhile noting it is not that rare, although inconvenient to access.

It is believed majorite makes up a substantial proportion of the Earth's lower transition zone and uppermost lower mantle, 550-900 kilometres below the Earth's surface. Under high pressure and temperature the mineral absorbs and stores oxygen. As it is drawn towards the Earth's surface by convection currents, pressure and temperature drops, the mineral breaks down and releases the oxygen. It is thought the species stores large amounts of this oxygen, and contributes to keeping the Earth's surface moist and habitable. It only proves how the study of small things can lead to significant discoveries.

Ringwoodite is a high pressure polymorph of olivine with a spinel structure. In some chondrite meteroites it occurs in veinlets cutting the matrix, and replacing olivine during high shock events, or as fine grained polycrystalline aggregrates. In the Coorara Meteorite it is found as purple grains set in a matrix of fine grained garnet.

It is also a common mineral in the Earth's mantle, 525-660 below the surface. Ringwoodite and Wadleysite hold large amounts of water in their crystal structure, and it is thought these minerals play a significant role in the circulation of this part of the mantle.

Other Regions, Features and Areas containing this locality

References