Pyroxenes are a group of the 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 thusly 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 mantle of Earth is composed mainly of olivine and pyroxene.

Some pyroxenes:

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