Enstatite

• Amblystegit
• Chladnit
• Ficinit
• Orthoenstatit
• Paulit
• Peckhamit
• Protobastit
• Shepardit
• Victorit

The mineral enstatite is a common chain silicate from the group of pyroxenes with the idealized composition Mg 2 [ Si2O6 ]. It forms a mixed batch with ferrosilite ( Fe2 2 [ Si2O6 ] ). Within this series, all compositions with more than 1 and less than 0.1 mg Ca per formula unit are referred to as enstatite, all other generally known as hypersthene.

Enstatite is colorless or pale yellow, green, olive or brown in color, transparent to opaque with vitreous luster on crystal surfaces and pearlescent on cleavage surfaces. The crystals are of prismatic to fibrous habit, often twinned lamellar to { 100} and can be up to 50 cm long. He shows a good cleavage parallel to the prism faces { 210 }, where intersect the cleavage planes at an angle of 88 °. This distinguishes their cleavage planes cut it from similar amphiboles at an angle of about 120 °.

Enstatite is a common rock forming mineral of the mantle ( peridotite ), the lower crust ( granulite ), basic igneous rocks ( gabbro, pyroxenite ) and granulite metabasites ( granulites ), metapelites and metamorphic Kalksilikatgesteine ​​. In addition, there is a component of enstatite chondrites and Aubriten, rare classes of stone meteorites. Also on the surface of some asteroids such as ( 44) Nysa, (64 ) and Angelina (216 ) Kleopatra this hard mineral was detected.

Etymology and history

The name comes from the Greek ( enstates = enemy, adversary ) and refers to the fact that enstatite is almost infusible.

Other obsolete terms were used for partially or completely converted into other minerals enstatite:

• Agalit: Probably partly converted Talk enstatite
• Bastit, Schillerspat: In serpentine, talc and possibly anthophyllite converted enstatite
• Diaclasit, Germarit, Phastin: ' Converted enstatite
• Szaboit: partially converted enstatite

First described and named the mineral was in 1855 by Gustav Adolf Kenngott. As a type locality of the mountain Zdar applies to Ruda nad Moravou ( German Eisenberg an der March ) in the Czech Republic, as the material for chemical analysis came from there.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the enstatite belonged to the mineral class of " silicates and Germanates " and then to the Department of " chain silicates and phyllosilicates ( inosilicates ) " where he along with Donpeacorite, ferrosilite and Nchwaningit independent subset of " orthopyroxenes " within the pyroxene group was formed.

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the enstatite also in the class of " silicates and Germanates " and there in the department of " chains and chain silicates ( inosilicates ) " one. This division, however, is further subdivided by the structure of the silicate chains, and of belonging to larger mineral families, so that the mineral according to its composition and structure in the subsection " chain and chain silicates with 2- periodic single chains Si2O6; Pyroxene family " is to find where it is named as the " orthopyroxenes -. Enstatitgruppe "with the System No. Forms 9.DA.05 and the other members Akimotoit, Donpeacorite and ferrosilite.

The mainly common in English-speaking classification of minerals according to Dana assigns the enstatite in the class of " silicates and Germanates " and there in the department of " chain silicate minerals " one. Here he is with ferrosilite and Donpeacorite in the group of " orthopyroxenes " with the system no. 65.01.02 within the subdivision " chain silicates: Simple unbranched chains, W = 1 with chains P = 2" to find.

Varieties and modifications

The compound Mg 2 [ Si2O6 ] is polymorphic. In addition to the orthorhombic enstatite occur nor the monoclinic modification Clinoenstatite and also orthorhombic high-temperature modification protoenstatite.

Well-known varieties are:

• Bronzite has its iron admixtures a typical bronze color.
• Lime - Bronzite is a calcium - containing variety
• Vanadium Bronzite contains admixtures of vanadium

Education and Locations

Enstatite forms in ultrabasic magma rocks such as gabbros and peridotites. Through metamorphosis, it may form in marble. Accompanying minerals include diopside, clinopyroxene, olivine, phlogopite, pyrope and spinel.

Overall, enstatite so far (as of 2011) are detected at around 580 localities. Apart from its type locality Eisenberg an der March enstatite has been found in several places in Bohemia and Moravia.

In Germany, found the mineral in St. Blaise and dead moss in Baden- Württemberg; in Swabia, Franconia and the Upper Palatinate in Bavaria; in Bad Harzburg in Lower Saxony; Niederbachem in North Rhine -Westphalia; many places in the Eifel area in Rhineland -Palatinate and near Chemnitz and in the Ore Mountains in Saxony.

In Austria enstatite could be found among others at Pauliberg in Burgenland, in the Tyrolean municipality Wildschönau and at several locations in Carinthia, Lower Austria, Salzburg and Styria.

In Switzerland, the mineral previously occurred in Utzenstorf (Bern), Tafers (Freiburg), Châtillens ( Vaud), Saas -Almagell (Valais ), and at several places in the cantons of Grisons and Ticino to.

Other localities include Algeria, Antarctica, Argentina, Azerbaijan, Australia, Botswana, Brazil, Chile, China, Finland, France, Ghana, Greece, Greenland, India, Israel, Italy, Japan, Yemen, Canada, Kazakhstan, Lesotho, Libya, Madagascar, Mexico, Mongolia, Myanmar, Namibia, New Caledonia, New Zealand, Nigeria, Norway, Oman, Pakistan, Papua New Guinea, Peru, Poland, Portugal, Republic of Congo, Romania, Russia, in the Western Sahara, the Solomon Islands, Sweden Zimbabwe, Slovakia, Spain, Sudan, South Africa, Tajikistan, Tanzania, Turkey, Ukraine, the United Kingdom ( UK) and the United States of America (USA).

Even in rock samples from the Mid-Atlantic Ridge and the East Pacific Rise and outside the earth on the moon ( landing site of Apollo 15 mission ) and in the tail of comet Wild 2 material enstatite was found.

Sites for the variety Bronzite include Bad Harzburg in the resin, Kraubath in Styria, bushveld in Transvaal.

Crystal structure

Enstatite crystallized in the orthorhombic space group Pbca ( Raumgruppen-Nr. 61) with the lattice parameters a = 18.24 Å; b = 8.82 Å; c = 5.18 Å, and eight formula units per unit cell.

Use

Transparent green crystals are processed into semi-precious stones.