majorite
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Majorite is a mineral found in the mantle of the Earth. Its chemical formula is Mg3(MgSi)(SiO4)3. It is a type of garnet, distinguished from other garnets in having silicon in octahedral as well as tetrahedral coordination. Majorite was first described in 1970 from the Coorara Meteorite of Western Australia and has been reported from various other meteorites in which majorite is thought to result from an extraterrestrial high pressure shock event. Mantle-derived xenoliths containing majorite have been reported from potassic ultramafic magmas on Malaita Island on the Ontong Java Plateau in the
Key facts
- Mineral.name
- Majorite
- Mineral.image
- Majorite.jpg
- Mineral.category
- Nesosilicates
- Mineral.formula
- Mg3(MgSi)(SiO4)3
- Mineral.IMAsymbol
- Maj
- Mineral.strunz
- 9.AD.25
- Mineral.system
- Cubic
- Mineral.class
- Hexoctahedral (mm) H-M symbol: (4/m 2/m)
- Mineral.symmetry
- Iad or tetragonal I41/a for pure MgSiO3
- Mineral.unit cell
- a = 11.52 Å; Z = 8
- Mineral.color
- Purple, pale yellowish brown, colorless
- Mineral.habit
- Microcrystalline aggregates; acicular to equant grains in narrow veinlets
- Mineral.cleavage
- None
- Mineral.mohs
- 7–7.5
- Mineral.luster
- Vitreous
- Mineral.diaphaneity
- Semitransparent
- Mineral.gravity
- Measured at about 4; 3.51 (calculated for pure MgSiO3)
- Mineral.opticalprop
- Isotropic
via Wikipedia infobox
~2 min read
Encyclopedic overview
4 sectionsContents
- Synthetic magnesium endmember majorite
- In the mantle
- See also
- References
Majorite is a mineral found in the mantle of the Earth. Its chemical formula is Mg3(MgSi)(SiO4)3. It is a type of garnet, distinguished from other garnets in having silicon in octahedral as well as tetrahedral coordination. Majorite was first described in 1970 from the Coorara Meteorite of Western Australia and has been reported from various other meteorites in which majorite is thought to result from an extraterrestrial high pressure shock event. Mantle-derived xenoliths containing majorite have been reported from potassic ultramafic magmas on Malaita Island on the Ontong Java Plateau in the southwest Pacific Ocean.
==Synthetic magnesium endmember majorite== Pure synthetic magnesium majorite (MgSiO3) is polymorphous with enstatite, and akimotoite. Majorite is a member of the garnet group. It has Mg in eight-coordination with oxygen; it also has both Mg and Si in octahedral (6) coordination; and Si in tetrahedral (4) coordination with oxygen. Unlike most garnets, which are cubic, pure MgSiO3 majorite is tetragonal.
Excerpted from Wikipedia’s “majorite” article, available under the CC BY-SA 4.0 licence.