ENSTATITE

common silicate mineral in the pyroxene family. It is the stable form of magnesium silicate (MgSiO3, often with up to 10 percent iron) at low temperatures. See orthopyroxene. The other forms of magnesium silicate are protoenstatite, which occurs at very high temperatures, and clinoenstatite, which occurs in unstable form at low temperatures. Enstatite and protoenstatite crystallize in the orthorhombic system (three unequal axes at right angles to each other); clinoenstatite crystallizes in the monoclinic (three unequal axes with one oblique intersection). Clinoenstatite forms a series with clinoferrosilite that is analogous to the enstatiteferrosilite series.