Pyroxene

The pyroxenes are a group of important rock-forming silicate minerals found in many igneous and metamorphic rocks. They share a common structure comprised of single chains of silica tetrahedra and they crystalise in the monoclinic and orthorhombic system. Pyroxenes have the general formula XY(Si,Al)2O6 (where X represents calcium, sodium, iron+2 and magnesium and more rarely zinc, manganese and lithium and

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Y represents ions of smaller size, such as chromium, aluminium, iron+3, magnesium, manganese, scandium, titanium, vanadium and even iron+2).

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Although aluminium commonly substitutes for silicon in other silicates, it is not a common substitution in the pyroxene.

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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 they were impurities in the glass, hence the name "fire strangers".

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However, they are simply early forming minerals that crystallized before the lava erupted.

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The upper mantle of Earth is composed mainly of olivine and pyroxene. A piece of the mantle is shown in Figure 1 (the pyroxene is the black crystal) showing the expected composition of 60% olivine and 30% pyroxene.

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Silicate minerals: The silicate minerals make up the largest and most important class of rock-forming minerals. They are classified based on the structure of their silicate anion group....

Igneous: REDIRECT Igneous rock...

Metamorphic: The term Metamorphic can be associated with a number of meanings:-...