Edenite is a double chain silicate mineral of the

amphibole Amphibole () is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMA symbol is A ...

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.

Occurrence

Edenite has been found primarily in metamorphic rocks, occurring in pods of other magnesium rich minerals within a marble formation or with garnet rich

lherzolite Lherzolite is a type of ultramafic igneous rock. It is a coarse-grained rock consisting of 40 to 90% olivine along with significant orthopyroxene and lesser amounts of calcic chromium-rich clinopyroxene. Minor minerals include chromium and alu ...

s from deep within the Earth's crust. Thus, finding edenite in the field can indicate high temperature regional metamorphism of the surrounding rocks.

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. This makes edenite a good candidate for use in chlorine isotope fractionation in amphibole-bearing rocks. Many synthetic variations of edenite are also used in geochemical research to produce a

boron Boron is a chemical element with the symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the ''boron group'' it has th ...

analogue of fluoroedenite.

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.

References

{{Reflist Amphibole group Monoclinic minerals Minerals in space group 12