Enstatite: The mineral Enstatite information and pictures

About

Enstatite forms series with the rare mineral Ferrosillite (Fe₂Si₂O₆). Pure Enstatite (without any at all iron) is not common, and pure Ferrosillite (without any magnesium) is extremely rare. A common intermediary member of this series is known as Hypersthene, with a chemical formula of (Mg,Fe)₂Si₂O₆. Although the term Hypersthene has been discredited by the IMA in 1998, it is still commonly used by many reference guides and is labeled as such in many collections.

Pure Enstatite is transparent and lightly colored; the iron content is responsible for the darker colors and increased opacity.

Crystal Forms & Aggregates

As disordered aggregates of rectangular crystals. May also occur in single prismatic and stubby crystals, which may be well-terminated. Also as cleavage fragments, as platy groupings, fibrous masses, radiating, and lammelar. Crystals are partially hollow or dissolved in some localities.

Striking Features

Luster and cleavage angles

Environment

As a rock-forming mineral in various igneous environment, and in metamorphosed Serpentine deposits. Also as a constituent of some meteorites.

Varieties

✓ common · ✗ uncommon

Bronzite— Dark brown or greenish-brown, weathered variety of Enstatite with a high luster. It often contains impurities of Hematite and Goethite, which are responsible for its bronze-like color sheen.
Chrome-Enstatite— Deep forest-green, chromium-rich variety of Enstatite.
Hypersthene— Iron-rich variety of Enstatite, which was historically classified as an individual mineral species until 1998, when it was discredited by the IMA. The chemical form of Hypersthene is (Mg,Fe)₂Si₂O₆.

Polymorphs

Clinoenstatite

Uses

The variety Bronzite is used as a minor gemstone. It often contains inclusions of highly reflective minerals, such as Hematite and Goethite, which give it a bronze-like effect when polished (hence its name). Polished Bronzite may also exhibit asterism or cat's eye effect.

Noteworthy Localities

A classic Bronzite occurrence is the chrome mines of Kraubath, Styria, Austria. Small, transparent crystals come from Mont-Dore, Auvergne, France; and an exceptionally gemmy olive-green form comes from Mogok, Mynamar (Burma); and from the Kilosa District, Morogoro, Tanzania.

In the U.S., localities include the the Tilly Foster Mine, Brewster, Putnam Co., New York; Gore Mountain, Warren Co., New York; the Wood's Chrome Mine, Texas, Lancaster Co., Pennsylvania; Summit Rock, Klamath Co., Oregon; and Nain, Labrador, Canada. Good Bronzite comes from the Bare Hills, Baltimore Co., Maryland; and Webster, Jackson Co., North Carolina.