Fibrous sprays of pistachio green Epidote crystals from Russia.
CHEMISTRY Ca2(Al,Fe)3(SiO4)3(OH) Hydrous calcium, aluminum - iron silicate
CRYSTALLOGRAPHY Monoclinic
CRYSTAL GROWTH AND HABITS Epidote is prismatic, commonly forming long, slender, grooved crystals. It also forms thin crusts or microscopic crystals; also fibrous to massive.
COLOR AND OTHER OPTICAL PROPERTIES Epidote is often pistachio green but can also be yellowish green to brownish in color. It is transparent to translucent and strongly pleochroic green to brown.
HARDNESS 6 - 7
SPECIFIC GRAVITY 3.3 - 3.5
LUSTER Vitreous
STREAK White
BREAKABILITY Epidote has one very good basal cleavage and uneven fracture.
OCCURRENCE Epidote is a very common mineral that is often formed by the weathering of feldspars, pyroxenes, amphiboles and biotite.
ASSOCIATED MINERALS Chlorite, Quartz