Epidote is an orthosilicate mineral, hydrated calcium iron aluminum silicate (Ca2Fe3(Al2O)(OH)(Si2O7)[Si2O4]).
It is found in metamorphic and igneous rocks as monoclinic system prismatic crystals and fibrous or granular masses;
it is typically pistachio green, glassy, and brittle. Certain large crystals,
7.5–25cm (3–10in), are collector's items.
Hardness 6–7; relative density 3.4.
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