Enstatite
This is an example of the pleochroism shown by Enstatite
containing about 15% iron (gamma refractive index about
1.680). With a single polarizing filter oriented with its
vibration direction parallel to the long axis of the crystal the crystal appears
greenish. This crystal is from a sample of sand at the mouth
of Willapa Bay at Cape Shoalwater.
Transmitted Linear Polarized Light, Single Polarizing Filter Parallel to the long axis.
Definition/Function:
Enstatite is one of the orthopyroxenes (Mg,Fe2+SiO3).
Significance in the Environment:
Characteristic Features:
Enstatite with about 15% iron is an orthorhombic crystal with gamma green and alpha pink
pleochroism. the crystals tend to elongate along
gamma so this refractive index is generally easy to measure and is a good indicator of
the iron content in this mineral. The gamma refractive
index ranges from 1.658 to 1.788. The alpha refractive index ranges from 1.650 to 1.768
and the beta refractive index from 1.653 to 1.770.
Enstatite can be distinguished from andalusite by andalusite's tendency to elongate
along alpha rather than gamma.
Associated Particles:
References:
Deer, W. A., R. A. Howie, and J. Zussman, AN INTRODCUTION TO THE ROCK-FORMING MINERALS,
ISBN 0-582-30094-0, pp. 155-165, 1992.
