Pyroxenes (silicates): Enstatite
Diagnostic card.
Mg 2 Si 2 O 6
Diamond orthogonality
Hardness 5-6
Specific weight 3,1-3,2
Cleavage is difficult
Cracked shell
Color is colorless, differently colored
Powder color light greenish-gray
Glitter glass
Crystals of enstatite are rhombic, usually translucent, with glass shine, on cleavage surfaces - pearly. Well-formed crystals are rare; The mineral is much more often found in the form of massive or thin-plate aggregates. Coloration light greenish-gray, green, sometimes brown.
Chemical composition. Magnesium oxide (MgO) 30%, ferrous oxide (FeO) 9%, calcium oxide (CaO) up to 2.5%, ferric oxide (Fe2O3) 0.5%, alumina (Al2O3) 2.6%, silica ( SiO2) 54.50%. The shape of the crystals. Prismatic, tabular. Crystal structure. Simple chains of ions. Class of symmetry. Rhombo-bipyramidal. Cleavage. Good in prism, the angle between cleavage planes is 85 ° . Aggregates. Usually dense, granular.
Diagnostic signs.
Enstatite without any impurities can not be affected by acids and does not melt in the flame of a candle. Melts with difficulty. Behavior in acids. Does not dissolve.
Origin.
Enstatite is common in ultrabasic and basic rocks of magmatic origin, such as peridotites, pyroxenites and gabbros; In metamorphic rocks of granulite type and serpentinites.
Deposits and applications.
The most interesting specimens come from the USA, South Africa, Canada, Germany, Norway, Burma and Sri Lanka. The latter have asterism. In Italy, specimens of collective interest are mined in Sondalo, Vattelino, in the Alto-Adige region. Enstatite of good transparency is used in jewelry business. A number of enstatite. This series includes bronzite (the extreme member of the series containing 5 to 13% iron oxide), hypersthene (more than 13%), and ferrosilite, the final term of the series in which only iron is present. Clinoenstatite is a monoclinic analogue of enstatite. Forms small crystals of prismatic or tabular habit; Thin-lamellar masses are also common. The color is either absent or varies from brown to light green. Glitter is glass. This rare mineral is found in some igneous rocks. It is installed in volcanic porphyrites in Vogelkop (Indonesia).
Enstatite. Kukhilal, SW Pamir, Tajikistan. Photo: © А.А. Evseev.
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