Crystal Epidote

Chemical Formula

Ca₂(Al,Fe)₂(SiO₄)₃(OH)

Composition

Basic calcium aluminum iron silicate.

Color

Light to dark-green, olive-green, brownish-green, yellowish-green, yellow, brown, black. Transparent forms can be strongly pleochroic with a greenish color on one angle and brownish color on the other angle.

Streak

White

Hardness

6 - 7

Crystal System

Monoclinic

Crystal Forms 
and Aggregates

Usually in long slender prismatic crystals; also in thick tabular crystals. Crystals are sometimes striatedand may have interesting wedge-shaped terminations. They also may have etchings or growth layers, and may contain late-growth small crystals layers growing upon a larger crystal. Also columnarreticulated, acicular, radiating, in fan-shaped and wheat sheaf crystal groups, and in long, slender fragile interconnected crystal groupings. May also form as a thin microcrystal crusting and may be massive. 
 

Transparency

Transparent to nearly opaque

Specific Gravity

3.3 - 3.6

Luster

Vitreous

Cleavage

1,1

Fracture

Uneven

Tenacity

Brittle

In Group

Silicates; Sorosilicates

Striking Features

Greenish color and common crystal habits

Environment

Epidote occurs in several different environments. It is found in hornfels and skarns in contact metamorphic rocks, and in metamorphosed limestone and in schists in regional metamorphic rock. It is also found in igneous rock in basalt and diabase, and is occasionally found in granite pegmatites.
 

Rock Type

Igneous, Sedimentary, Metamorphic

Popularity (1-4)

2

Prevalence (1-3)

1

Demand (1-3)

1