A magnesium-rich orthorhombic amphibole with perfect (210) cleavage and a colour which varies from white to various shades of green and brown. It is a comparatively rare metamorphic mineral which occurs as slender prismatic needles, in fibrous masses, and sometimes in asbestiform masses. Anthophyllite may occur together with calcite, magnesite, dolomite, quartz, tremolite, talc, or enstatite in metacarbonate rocks; with plagioclase, quartz, orthopyroxene, garnet, staurolite, chlorite, or spinel in cordierite-anthophyllite rocks; and with quartz and hematite in metamorphosed iron formations and with talc, olivine, chlorite, or spinel in metamorphosed ultrabasic rocks. Anthophyllite is distinguished from other amphiboles by optical examination or by x-ray diffraction, and from other minerals by its two cleavage directions at approximately 126° and 54°.