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Majorite is a type of mineral found in the upper mantle of the Earth. Its chemical formula is Mg3(Fe, Al,Si)2(SiO4)3. Majorite was first described from the Coorara Meteorite of Western Australia and has been reported from various other meteorites. Mantle derived xenoliths containing majorite have been reported from potassic ultramafic magmas on Malaita Island on the Ontong Java Plateau Southwest Pacific.
A significant property of majorite is that under conditions of high pressure and temperature as exist in the mantle the mineral tends to absorb and store oxygen. However when the temperature and pressure decrease as would occur when the majorite is drawn up toward the surface of the Earth by convection currents the mineral breaks down and releases the oxygen. Recent research has suggested that the total amount of oxygen stored in majorite in the mantle is likely quite large and may in fact contribute to keeping the earth's surface moist and habitable.
1. ^ http://www.mindat.org/min-2546.html Majorite on MinDat