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Epidote
Current inventory:  0 gems
 

Chemistry:  Ca₂(Al,Fe)₃Si₃O₁₂(OH)

Discovered in 1801;   IMA status: Valid (pre-IMA; Grandfathered).
The name Epidote is derived from the Greek word epidosis meaning addition or increase because the base of the crystal's prism has one side longer than the other.

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/C.23-20

Nickel-Strunz 10th Ed. ID:

9.AD.25

9 : SILICATES (Germanates)
A : Nesosilicates
D : Nesosilicates without additional anions; cations in [6] and/or greater coordination
25 : Garnet Group

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

Crystals prismatic to 35cm. Fibrous, coarse to fine granular, massive

Twinning:

On [100], contact, lamellar, common

Physical Properties

Cleavage:

[001] Perfect, [100] Imperfect

Fracture:

Irregular/Uneven

Tenacity:

Brittle

Hardness (Mohs):

6.0 - 7.0

Density:

3.38 - 3.49 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Pistachio-Green to pale Green, Yellow, Yellowish Green, Greenish Yellow, Greenish Black;

Transparency:

Transparent, Opaque

Luster:

Vitreous, Pearly

Refractive Index:

1.715 - 1.797  Biaxial ( - )

Birefringence:

0.019 - 0.046

Dispersion:

0.019; Strong; r > v

Pleochroism:

Strong; X = colorless, pale yellow, pale green; Y = greenish yellow; Z = yellowish green

Occurances

Geological Setting:

Regional and contact metamorphic rocks. Saussuritization (alteration of plagioclase).

Type Locality:

Bourg d'Oisans, Isère, Rhône-Alpes, France

Year Discovered:

1801

View mineral photos:

Epidote Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Epidote is a rare member of the Epidote Group of minerals that includes Allanite, Clinozoisite, Epidote, Hancockite, Mukhinite, Piedmontite, Tanzanite, Thulite and Zoisite. Epidote is usually so dark green that it appears nearly black. Smaller gems can be very bright green however. It is found in many locations throughout the world (including Colorado), but gem quality crystals are somewhat rare. Epidote is usually a fibrous, nearly opaque mineral that would only yield catseyes or cabachons so faceted gems are rare.

There are many locations worldwide were Epidote is found but few produce gem quality crystals. A few gem locations are Corinthia and Salzburg, Austria; Minas Gerais, Brazil; Provence-Alpes-Côte d'Azur & Bourg d'Oisans, Isère, Rhône-Alpes, France; Aosta Valley, Italy; Baltistan & Tormiq, Pakistan; Ticino, Switzerland; Chaffee County, Colorado, USA and Lamoille & Orleans Counties, Vermont, USA.
 

  
Epidote Garnet gems for sale:

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