Epidote

Ca2(Al,Fe)3(SiO4)(Si2O7)O(OH)

Distinguished by a distinctive pistachio-green color, epidote is a monoclinic sorosilicate with the formula Ca2(Al,Fe)3(SiO4)(Si2O7)O(OH). It forms during metamorphism and hydrothermal alteration across a wide range of rock types and is an important constituent of greenstone belts. The mineral is translucent with a vitreous luster, a gray streak, and perfect {001} cleavage, occurring as prismatic, columnar, or fibrous crystals. Its Mohs hardness is 6 to 7 and its specific gravity 3.25 to 3.50. Well-formed epidote crystals are collected as specimens, and the mineral's characteristic yellow-green hue makes it readily identifiable in the field. A specific gravity of 3.25 to 3.50 and a prismatic to fibrous habit round out its diagnostic profile.

Epidote is a common metamorphic and hydrothermal mineral recognizable by its distinctive pistachio-green color. It forms in a wide range of rock types during metamorphism and is an important constituent of greenstone belts.

Crystal System Monoclinic
Mineral Class 09 Silicates
Mohs Hardness 6.0-7.0
Specific Gravity 3.25-3.50
Color Pistachio green, yellowish-green, dark green
Luster Vitreous
Streak Gray
Cleavage Perfect {001}
Fracture Uneven
Transparency Translucent
Crystal Habit Prismatic, columnar, fibrous

Mohs Hardness

Mohs Hardness: 6.0 – 7.0
1 Soft10 Hard
Epidote has a Mohs hardness of 6–7 on the 1–10 mineral hardness scale.
Mohs Hardness Reference Mineral
1 Talc
2 Gypsum
3 Calcite
4 Fluorite
5 Apatite
6 Orthoclase
7 Quartz
8 Topaz
9 Corundum
10 Diamond

Crystal System

Monoclinic
Epidote crystallizes in the Monoclinic crystal system.
Property Value
Crystal System Monoclinic
Axial Relationships a ≠ b ≠ c, α = γ = 90°, β ≠ 90°

Frequently Asked Questions

What is the hardness of Epidote?
Epidote has a Mohs hardness of 6.0-7.0.
What crystal system does Epidote belong to?
Epidote crystallizes in the Monoclinic crystal system.
What color is Epidote?
Epidote is typically Pistachio green, yellowish-green, dark green.
What type of luster does Epidote have?
Epidote exhibits a Vitreous luster.
What is the chemical formula of Epidote?
The chemical formula of Epidote is Ca2(Al,Fe)3(SiO4)(Si2O7)O(OH).