Epidote

epidote
Rough epidote from Armenia

Epidote is fairly dense, fragile with distinct cleavage and is rarely cut as a gemstone. Epidote crystals are yellow, green, or dark brown columnar prisms, with faces finely striated parallel to the crystal’s length. Pleochroism is strong, showing either yellow, green, or brown. Rock composed mainly of epidote may be polished or tumbled and sold as unakite.

Dark green crystals occur in the Austrian and French Alps. Epidote is also found in the former USSR, Italy, the island of Elba (Italy), Mozambique and Mexico.

Epidote Pictures

Epidote Mineral

Cause of Color :

Iron

Chemical Composition :

Calcium Aluminium Silicate with Iron – Ca2(Fe,Al)3(SiO4)3(OH)

Classification / Type :

The epidote group is an isomorphous group comprising the following minerals:

  1. Zoisite
  2. Clinozoisite
  3. Epidote
  4. Piedmontite
  5. Hancockite
  6. Allanite
Crystal System / Forms :

Monoclinic System / Prismatic crystals with vertical striations.

Cuts & Uses :

Facetted, cabochons, etc.

Dispersion : 0.030
Hardness : 6.5
Lustre : Vitreous
Magnification :

Parallel needle inclusions, strong doubling of facet edges and inclusions, color zoning.

Optic Character :

Anisotropic, D.R.; Biaxial negative (may show pseudo-uniaxial)

Pleochroism : Strong (green, brownish red, yellow)
Refractive Index / Birefringence :

1.729 – 1.768 / 0.019 – 0.045

Simulants (with separation tests) :

Tourmaline (R.I., S.G., spectrum), Kornerupine (R.I., S.G., spectrum), Sillimanite (R.I., S.G., spectrum, pleochroism)

Sources :

U.S.A., Sri Lanka, India, Myanmar, Madagascar, Austria, Norway, Switzerland.

Specific Tests :

The strong reddish brown pleochroic color is often mistaken for a color change phenomena.

Spectrum :

455nm, 475nm (Directional)

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