epidote (redirected from Pistacite)

epidote

Any of a group of colourless to green or yellow-green silicate minerals with the general chemical formula A₂B₃(SiO₄)(Si₂O₇)O(OH), in which A is usually calcium (Ca) and B is generally aluminum (Al), although other elements are sometimes substituted. The epidote minerals occur as reaction products of other (earlier) minerals in low-grade (formed under relatively low-temperature, low-pressure conditions), regionally metamorphosed rocks, where their occurrence is used as an indicator of metamorphic grade.