The pyroxenes are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. They share a common structure consisting of single chains of silica tetrahedra and they crystallize in the monoclinic and orthorhombic systems. 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 Y represents ions of smaller size, such as chromium, aluminium, iron+3, magnesium, manganese, scandium, titanium, vanadium and even iron+2). Although aluminium substitutes extensively for silicon in silicates such as feldspars and amphiboles, the substitution occurs only to a limited extent in most pyroxenes.

The name pyroxene comes from the Greek words for fire (πυρ) and stranger (ξένος). Pyroxenes were named this way because of 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". However, they are simply early-forming minerals that crystallized before the lava erupted.

The upper mantle of Earth is composed mainly of olivine and pyroxene. A piece of the mantle is shown at right (orthopyroxene is black, diopside (containing chromium) is bright green, and olivine is yellow-green) and is dominated by olivine, typical for common peridotite. Pyroxene and feldspar are the major minerals in basalt and gabbro.

Read more about Pyroxene:  Chemistry and Nomenclature of The Pyroxenes, Pyroxene Minerals

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... is an ultramafic igneous rock consisting essentially of minerals of the pyroxene group, such as augite and diopside, hypersthene, bronzite or enstatite ... and the websterites which contain both pyroxenes ... The pyroxene-rich rocks which result from the contact metamorphism of impure limestones are described as pyroxene hornfelses (calc-silicate hornfelses) ...
Amphibolite Facies - Uralite
... autogenic hydrothermal circulation their primary mineralogy of pyroxene and plagioclase, etc ... The texture is distinctive, the pyroxene altered to fuzzy, radially arranged actinolite pseudomorphically after pyroxene, and saussuritised plagioclase ...
Pyroxenite Lavas
... Purely pyroxene-bearing volcanic rocks are rare, restricted to spinifex textured sills, lava tubes and thick flows in the Archaean greenstone belts ... in-situ crystallisation and accumulation of pyroxene on the floor of a lava flow, creating the distinctive spinifex texture, but also occasionally mesocumulate and orthocumulate segregations ... chemistry of the magma differing only to favor crystallisation of pyroxene ...
... mostly of the two minerals, olivine and low-calcium (Ca) pyroxene (enstatite) it is named for occurrences in the Harz Mountains of Germany ... by the extraction of partial melts from the more pyroxene-rich peridotite called lherzolite ... If partial melting of the harzburgite continues, all of the pyroxene may be extracted from it to form magma, leaving behind the pyroxene-poor peridotite called dunite ...