Hypersthene

Chemistry: Form of Enstatite, with increased iron content, usually opaque.
Crystal system: Orthorhombic; rarely short prismatic crystals; lamellar masses common.
Color: Opaque; gem varieties dark brown with coppery iridescence; hypersthene enstatite: transparent brown.
Hardness: 5 - 6
Cleavage: Good: in 1 direction.
Specific gravity: 3.4 – 3.5
Refractive index: 1.6 – 1.79; 1.673 – 1.731; Biaxial negative (optic sign changes along the series); 0.014
Luster: Vitreous, pearly or silky.
Dispersion: Low
Dichroism: Pinkish to greenish.
Occurrence: Igneous and metamorphic, also from meteorites; Norway, Greenland, Germany, USA, Mexico.

Notes
Also called ferrohypersthene; varieties include bronzite; spectral line at 506nm and 547nm; cabochon, slab.