Edenite or edenitic hornblende is a double chain silicate mineral of the amphibole group with the general chemical composition NaCa2Mg5(Si7Al)O22(OH)2. Edenite is named for the locality of Edenville, Orange County, New York, where it was first described.[
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Occurrence
Edenite has been found primarily in Metamorphic rock rocks, occurring in pods of other magnesium-rich minerals within a marble formation or with garnet-rich from deep within the Earth's crust.
Uses and importance
While edenite is not important for commercial or industrial applications, it is often studied because of its unique chemical substitution properties. Results from research performed on amphiboles have shown that edenite is particularly suited for fitting chloride anions into its chemical framework.
Crystal habit
Edenite is a member of the monoclinic crystal system and is in the crystal class 2/m (space group C2/m).[ This means crystalline edenite is symmetrical around a two-fold rotation axis that is then reflected across a mirror plane perpendicular to the long axis of the mineral.][Klein, C., and Dutrow, B. (2007) The 23rd Edition of the Manual of Mineral Science, John Wiley and Sons, Inc. Hoboken, New Jersey, U.S.]
Optical properties
Edenite is a biaxial positive mineral. When viewed in thin section with a petrographic microscope, it is white-gray with pale green pleochroism in plane-polarized light. Under crossed polars, its interference colors range from first order gray to first order blue.[
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