Pyroxene is a silicate mineral with the general composition (Mg,Fe)SiO3. Though the basic formula is simple, it is said to be a complex class of minerals. The most common member of the group is augite, which forms dark crystals as a result of the iron and magnesium content. It is said to a ferromagnesian or "mafic" mineral which has a high crystallization temperature and is formed early in the Bowen reaction series.
The name pyroxene comes from the Greek words for fire and stranger. 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.(Wiki).
Lutgens & Tarbuck