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Pyroxenes are a group of rock-forming silicate minerals. They are comprised of single chains of silica tetrahedra and have the general formula XY(Si,Al)2O6. X represents calcium, sodium, iron+2 and magnesium and more rarely zinc, manganese and lithium.
Y represents ions of smaller size, such as chromium, aluminium, iron+3, magnesium, manganese, scandium, titanium, vanadium and even iron+2.
Although aluminium commonly substitutes for silicon in other silicates, it usually doesn't substitute for silicon in a pyroxene.
The name pyroxene comes from the Greek words for fire and stranger. It was named that way due to their presence in volcanic lavas, where they are sometimes seen as crystals embedded in volcanic glass; it was assumed that were impurities in the glass, hence the name "fire strangers".
However, they are simply early forming minerals that crystallized before the lava erupted.
The mantleThe mantle is the layer in the structure of the Earth that lies directly under the Earth's crust. It lies between 30 and 2,900 km below the surface. The boundary between the crust and the mantle is the Mohorovicic discontinuity, named for its discoverer, of Earth is composed mainly of olivineThe mineral olivine is a magnesium iron silicate with the formula (Mg,Fe)SiO in which the ratio of magnesium and iron varies between the two endmembers of the series: forsterite (Mg-rich) and fayalite (Fe-rich). It gives its name to the group of minerals and pyroxene.
Some pyroxenes:
- Clinopyroxenes (monoclinic)
- Aegirine (Sodium Iron Silicate)
- AugiteAugite is a mafic mineral described chemically as (Ca, Na)(Mg, Fe, Al)(Al, Si)O or calcium sodium magnesium iron aluminium silicate. Structurally, it is a solid solution of the pyroxene group which also contains diopside and hedenbergite. The crystals are (Calcium Sodium Magnesium Iron Aluminum Silicate)
- Clinoenstatite (Magnesium Silicate)
- Diopside (Calcium Magnesium Silicate, CaMgSi2O6)
- Esseneite (Calcium Iron Aluminum Silicate)
- Hedenbergite (Calcium Iron Silicate)
- HyperstheneHypersthene is a common rock-forming mineral belonging to the group of orthorhombic pyroxenes. It is found in igneous and some metamorphic rocks as well as in stony and iron meteorites. It forms a solid solution series with the minerals enstatite and ferr (Magnesium Iron Silicate)
- JadeiteJadeite is a pyroxene mineral with composition NaAlSiO. Jadeite is found only in metamorphic rocks that form under high pressure and relatively low temperature conditions. Associated minerals include: glaucophane, muscovite, lawsonite, aragonite, and quar (Sodium Aluminum Silicate)
- Jervisite (Sodium Calcium Iron Scandium Magnesium Silicate)
- Johannsenite (Calcium Manganese Silicate)
- Kanoite (Manganese Magnesium Silicate)
- Kosmochlor (Sodium Chromium Silicate)
- Namansilite (Sodium Manganese Silicate)
- Natalyite (Sodium Vanadium Chromium Silicate)
- Omphacite (Calcium Sodium Magnesium Iron Aluminum Silicate)
- Petedunnite (Calcium Zinc Manganese Iron Magnesium Silicate)
- Pigeonite (Calcium Magnesium Iron Silicate)
- SpodumeneSpodumene is a pyroxene mineral consisting of lithium aluminium inosilicate LiAl(SiO) and is a source of lithium. It occurs as colourless to yellowish ( triphane), purplish or lilac ( kunzite), yellowish-green, or emerald-green ( hiddenite) prismatic crys (Lithium Aluminum Silicate)
- Orthopyroxenes (Orthorhombic)
- HyperstheneHypersthene is a common rock-forming mineral belonging to the group of orthorhombic pyroxenes. It is found in igneous and some metamorphic rocks as well as in stony and iron meteorites. It forms a solid solution series with the minerals enstatite and ferr
- Donpeacorite (Manganese Magnesium Silicate)
- EnstatiteEnstatite is a common rock-forming mineral belonging to the group of orthorhombic pyroxenes. It is a magnesium silicate, MgSiO, often with a little iron replacing the magnesium. It forms a solid solution series with the minerals hypersthene and ferrosilit (Magnesium Silicate)
- Ferrosilite (Iron Magnesium Silicate)
- Nchwaningite (Hydrated Manganese Silicate)
- Schefferite , Ca(Mg,Fe,Mn)Si2O6
- Zinc schefferite , Ca(Mg,Mn,Zn)Si2O6
- Jeffersonite , Ca(Mg,Fe,Mn,Zn)Si2O6
- Leucaugite , Ca(Mg,Fe,Al)(Al,Si)2O