Augite

Augite is a very common mineral from the mineral class of " silicates and Germanates ". It crystallizes in the monoclinic crystal system with the chemical composition (Ca, Fe) (Mg, Fe) [ Si2O6 ] and developed short to long prismatic crystals, but also grained mineral aggregates of green, brown or black in color with gray-green stroke color. Very rarely, colorless augite ( Leukaugit ) are found.

With a Mohs hardness from 5 to 6.5 augite is one of the medium-hard minerals, it can be just a knife or steel file scratch.

Special Features

Before the blowpipe melts to black augite, often magnetic glass. He is generally only weakly attacked by acids, with the exception of hydrofluoric acid.

Etymology and history

Augite was the first time in 1792 by the German mineralogist Abraham Gottlob Werner described and named after the Greek word αὐγή eye, which means as much as gloss.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the augite belonged to the mineral class of " silicates and Germanates " and there to the general ward of the " chains and chain silicates ( inosilicates ) ", where he, together with aegirine, diopside Esseneit, hedenbergite, jadeite, Jervisit, Johannsenite, Kanoit, Klinoenstatit, Klinoferrosilit, Kosmochlor, Namansilit, Natalyit, omphacite, Petedunnit, pigeonite and spodumene formed the subgroup of clinopyroxene within the pyroxene group.

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the augite also in the class of " silicates and Germanates " and there in the department of " chains and chain silicates ( inosilicates ) " one. This division, however, is now more precisely divided according to the type of chains or belts education and the special relationship of some minerals, so that the mineral in accordance with the subdivision " chain and chain silicates with 2- periodic single chains Si2O6; Pyroxene family " is to find where it together with diopside, Esseneit, hedenbergite, Johannsenite and Petedunnit the ". Ca clinopyroxene, Diopsidgruppe "with the system no 9.DA.15 forms.

The classification of minerals according to Dana assigns the augite in the class of " silicates " and there in the department of " chain silicate minerals ." There he is, also together with diopside, Esseneit, hedenbergite, Johannsenite and Petedunnit, member of the " C2 / c clinopyroxene (Ca - clinopyroxene ) " with the system no. 65.1.3a within the subdivision " chain silicates: Simple unbranched chains, W = 1 with chains P = 2".

Modifications and varieties

As a Fassait augite or diopside variety is known with an increased iron and aluminum content.

As Jeffersonit refers to a manganese - and zinc-containing augite or diopside variety.

Education and Locations

Augite is a rock forming mineral that forms an essential Gemengteil in many and as an ancillary component in most igneous rocks such as basalt, diabase, gabbro, melaphyre and tuffs. Accompanying minerals include various minerals of the amphibole group, labradorite, leucite, olivine, orthoclase, sanidine and various minerals of the pyroxene group.

Worldwide could be detected at about 1,200 localities augite so far, so among other things in Egypt, Algeria, Antarctic, Argentina, Armenia, Azerbaijan, Australia, Bolivia, Brazil, Bulgaria, Chile, China, Costa Rica, Germany, El Salvador, Eritrea, Fiji, Finland, France, French Polynesia, Ghana, Greece, Greenland, Guadeloupe ( French West Indies ), Guinea, India, Iran, Israel, Italy, Japan, Yemen, in the Virgin Islands, Cameroon, Canada, Kazakhstan, Kenya, Kyrgyzstan, the Republic of Congo, Colombia, Libya, Madagascar, Mali, Malta, Morocco, Mexico, Montserrat, Namibia, New Caledonia, New Zealand, Norway, Oman, Austria, Pakistan, Papua New Guinea, Paraguay, Poland, Portugal, Romania, Russia, Western Sahara, in the Solomon Islands, Sweden, Switzerland, Sierra Leone, Slovakia, Spain, St. Lucia, St. Vincent and the Grenadines, South Africa, South Korea, Tanzania, Czech Republic, Turkey, Ukraine, Hungary, Uzbekistan, the United Kingdom ( UK ) and the United States of America (USA). In addition, augite is part of some stony meteorites.

It is worth mentioning, among others, the archaeological site at Clear Lake in Ontario (Canada), where crystals up to 15 cm in size were revealed. Am Laacher See in Rhineland -Palatinate ( Germany ) up to 5 cm large crystals were found.

Augite was also found in rock samples of the East Pacific Ridge - as well as extraterrestrial on the moon ( Mare Crisium, Mare Fecunditatis and Montes Taurus ) and Mars ( Valles Marineris ) augite was found.

Crystal structure

Augite crystallizes in the monoclinic space group C2 / c with lattice parameters a = 9.69 Å; b = 8.84 Å; c = 5.28 Å and 106.3 ° and β = 4 formula units per unit cell.

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