Mineral Species: Enstatite

Chemical Formula: MgSiO3

Chemical Name: Magnesium Silicate

Mineral Class: Inosilicate

Mineral Notes: Enstatite is a relatively common mineral found in metamorphic and some igneous rocks. It forms a solid solution series with Hypersthene and Ferrosilite. Enstatite is the magnesium end member, Ferrosilite the iron end member and Hypersthene is the intermediate member with around 50% iron and 50% magnesium. Enstatite is an orthopyroxene or a pyroxene with an orthorhombic symmetry. At high temperatures, the mineral's structure changes to a structure with a monoclinic symmetry, a clinopyroxene or more specifically, Clinoenstatite. Clinoenstatite is a polymorph of Enstatite, meaning that it has the same chemistry but a different structure. Enstatite has some ornamental and gemstone varieties. A weathered variety that has a submetallic luster and a bronze like colour is called "Bronzite". It is often used as an ornamental stone. An emerald green variety is called Chrome-enstatite and is cut for gemstones. The green colour is caused by traces of chromium. Enstatite has the potential to form in igneous rocks but the high abundance of iron in most magmas means that the result is usually Ferrosilite. As a result, Enstatite is more commonly seen in highly metamorphosed rocks called granulites. It commonly forms from the alteration and dehydration of the amphibole mineral Anthophyllite.

Description: The green colour of this Enstatite means that it contains a high degree of Chromium. The mineral forms flattened crystals that overlap on the surface of the matrix. Some weathering has changed the faces of the outward facing crystals to give them a very distinct bronze-like luster. The combination of chromium and bronze colouration is rare and makes this a very attractive and interesting specimen.

Location: Vezna, Czech Republic.