Cause of Color :
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:
Crystal System / Forms :
Monoclinic System / Prismatic crystals with vertical striations.
Cuts & Uses :
Facetted, cabochons, etc.
Parallel needle inclusions, strong doubling of facet edges and inclusions, color zoning.
Optic Character :
Anisotropic, D.R.; Biaxial negative (may show pseudo-uniaxial)
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)
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.
455nm, 475nm (Directional)