Epidote

Real mineral · common · Ca₂Al₂(Fe³⁺)(Si₂O₇)(SiO₄)O(OH)

Calcium iron aluminium silicate common in low to medium grade metamorphic rocks. Its characteristic pistachio green colour results from ferric iron. Forms as a secondary mineral in the alteration of plagioclase feldspar.

Identity

Formula

Ca₂Al₂(Fe³⁺)(Si₂O₇)(SiO₄)O(OH)

Chemical class

silicate

Also known as

Pistacite (pistachio-green variety)

Crystallography

Crystal system

monoclinic

Habits

prismatic, tabular, massive

Fracture

uneven

Physical properties

Mohs hardness

6.5

Density

3.45 g/cm³

Luster

vitreous

Colors

yellow-green, olive green, dark green, brown

Streak

gray

Transparency

transparent, translucent

Geology

Origins

metamorphic, hydrothermal

Host rocks

schist, gneiss, marble

Associated minerals

Quartz, Calcite, Chlorite, Garnet

Geography

Austria, Norway, Mexico, USA, Russia

Classification

Rarity

common

Gem quality

No

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