Enstatite
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Enstatite is named from the Greek word enstates meaning an opponent because of its high melting point.

Discovered in 1855; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Mg₂Si₂O₆

Magnesium Silicate

Molecular Weight:

200.78 gm

Composition:

Magnesium

24.21 %

Mg

40.15 %

MgO

Silicon

27.98 %

Si

59.85 %

SiO₂

Oxygen

47.81 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/F.02-10

Nickel-Strunz 10th Ed. ID:

9.AD.05

9 : SILICATES (Germanates)
D : Inosilicates
A : Inosilicates with 2-periodic single chains, Si₂O₆; pyroxene family
05 : Enstatite Group; Enstatite-Ferrosilite Series

Related to:

Pyroxene Group. Orthopyroxene Subgroup. Enstatite-Ferrosilite Series. Dimorphous with Clinoenstatite.

Members of Group:

Pyroxene Group: Canaanite, Clinopyroxene Subgroup, Orthopyroxene Subgroup

Members of Subgroup:

Orthopyroxene Subgroup: Donpeacorite, Enstatite, Ferrosilite

Varieties:

Bronzite, Chromian-Enstatite, Lime-Bronzite, Vanadinbronzite

Synonyms:

Amblystegite, Chladnite, Enstadite, Ficinite, O-enstatite, Orthobronzite, Orthoenstatite, Paulite, Peckhamite, Protobastite, Shepardite, Shepardite (of Rose), Victorite

Crystal Data

Crystallography:

Orthorhombic - Dipyramidal

Crystal Habit:

Crystals prismatic, to 40 cm; commonly lamellar, fibrous, or massive.

Twinning:

Simple and lamellar twinning on {100}

Physical Properties

Cleavage:

Good on {210}, (210) ^ (210) ~88°; partings on {100} and {010}

Fracture:

Irregular/Uneven

Tenacity:

Brittle

Moh's Hardness:

5.0 - 6.0

Density:

3.20 - 3.90 (g/cm³)

Luminescence:

Not Fluorescent

Radioactivity:

Not Radioactive

Optical Properties

Color:

White, grayish, yellowish, greenish, olive-green, brown; colorless in thin section

Transparency:

Transparent to Opaque

Luster:

Vitreous, pearly on cleavages

Refractive Index:

1.650 - 1.679  Biaxial ( + ) 

Birefringence:

0.009 - 0.011

Dispersion:

Weak to moderate; r < v

Pleochroism:

None

Occurances

Geological Setting:

In pyroxenites, peridotites, and dunites; in ultramafic inclusions in alkalic olivine basalts and kimberlite; in mafic volcanics, rarely in felsic volcanics. Characteristic of charnockites and the granulite metamorphic facies, in regionally metamorphosed rocks and metagabbros. Common in chondrite, achondrite, and stony-iron meteorites.

Common Associations:

Olivine, Phlogopite, Clinopyroxene, Diopside, Spinel, Pyrope

Common Impurities:

Fe, Ca, Al, Co, Ni, Mn, Ti, Cr, Na, K

Type Locality:

Unknown

Year Discovered:

1855

View mineral photos:

Enstatite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Enstatite is a member of the Orthopyroxene Group that also includes Bronzite and Hypersthene. It is found as colorless, gray, green, yellow and brown crystals. Enstatite is closely related to Bronzite which has slightly more iron content than Enstatite and is, as the name implies, a beautiful bronze color and has sub-adamantine luster. A very dark green to black Enstatite cat's eye is also available and a chrome green Chromian-Enstatite is rarely found.

Enstatite is found in many locations worldwide but only a few produce gem quality crystals. Two of the best known locations are Embilipituya, Sri Lanka and Mbeya, Tanzania. Enstatite is also commonly found in stony and iron meteorites.

Distribution: Prominent localities for well-studied material include: from · Zdár (Zdjarberg), Czech Republic. At Ødegården and Kjörrestad, Bamble, Norway. From The Lizard, Cornwall, England. At Dawros, County Connaught, Ireland. From Kupferberg, Bavaria, and the Bellerberg volcano, two km north of Mayen, Eifel district, Germany. At Kraubath, Styria, Austria. Fine crystals from Mbeya, Tanzania. At Liahobong, Lesotho. In the USA, at Webster, Jackson County, and on Corundum Hill, Macon County, North Carolina; at Wood's chrome mine and Texas, Lancaster County, and elsewhere in Pennsylvania. Gem material from Embilipituya, Sri Lanka.
 

  
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