Majorite
| Majorite | ||
|---|---|---|
Specific gravity Measured at about 4; 3.51 (calculated for pure MgSiO3) | | |
| Optical properties | Isotropic | |
| Refractive index | n = 1.87 – 1.92 (calculated) | |
| Birefringence | slight | |
| References | [2][3][4][5] | |
Majorite is a type of garnet
Synthetic magnesium endmember majorite
Pure synthetic magnesium majorite (MgSiO3) is
In the mantle
Majorite is believed to be an abundant mineral in the lower transition zone and uppermost lower mantle of the Earth at depths of 550–900 km (340–560 mi). It forms complex solid solutions with other Al, Fe, and Ca-bearing garnets in this region.
All of the minerals of the Earth's mantle are made of oxygen as the principal anion. It has been reported that 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.[8]
See also
References
- S2CID 235729616.
- ^ a b Handbook of Mineralogy, Mineral Data Publishing
- ^ a b Majorite on MinDat
- ^ Majorite on Webmineral
- ^ The IMA Mineral List
- ^ Kenneth D. Collerson, et al., Rocks from the Mantle Transition Zone: Majorite-Bearing Xenoliths from Malaita, Southwest Pacific, Science 19 May 2000: Vol. 288. no. 5469, pp. 1215–1223 Abstract
- ^ Angel, R. J. (1989) Structure and twinning of single-crystal MgSiO3 garnet synthesized at 17 GPa and 1800-degrees-C, American Mineralogist, 74, 509-512.
- ^ Bryner, Jeanna: Huge Stockpile of Oxygen Found Deep Inside Earth, LiveScience, 1 October 2007 08:38 am ET [1]