Augit

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Augit
Augite - La Panchita Mine, Mun de La Pe, Oaxaca, Mexico.jpg
Augite crystal specimen from the La Pancita Mine, Oaxaca, Mexico
(comparative scale 1 "with notch at 1 cm)
General and classification
chemical formula
  • (Ca, Fe) (Mg, Fe) [Si 2 O 6 ]
  • (Ca, Mg, Fe) 2 Si 2 O 6
Mineral class
(and possibly department)
Silicates and Germanates
System no. to Strunz
and to Dana
9.DA.15 ( 8th edition : VIII / F.01)
65.01.03a.03
Similar minerals Hornblende
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group C 2 / c (No. 15)Template: room group / 15
Lattice parameters a  = 9.69  Å ; b  = 8.84 Å; c  = 5.28 Å
β  = 106.3 °
Formula units Z  = 4
Frequent crystal faces {100}, {010}, {110}, { 1 02}, { 1 11}
Twinning according to {100} and (010), often lamellar repeat twins
Physical Properties
Mohs hardness 5 to 6
Density (g / cm 3 ) measured: 3.19 to 3.56; calculated: 3.31
Cleavage clearly to good according to (110); Segregation after (100)
Break ; Tenacity shell-like to uneven; brittle
colour dark brown to black, greenish, brownish purple
Line color white, occasionally gray-green
transparency transparent to opaque
shine Glass gloss, resin gloss, matt
Crystal optics
Refractive indices n α  = 1.680 to 1.735
n β  = 1.684 to 1.741
n γ  = 1.706 to 1.774
Birefringence δ = 0.026 to 0.039
Optical character biaxial positive
Axis angle 2V = measured: 40 ° to 52 °; calculated: 48 ° to 68 °
Pleochroism light green-brown-green-blue-green
Other properties
Chemical behavior melts to black glass, slightly soluble in acids (except hydrofluoric acid )

Augite is a very common mineral from the mineral class of " silicates and germanates ". As clinopyroxene, it crystallizes in the monoclinic crystal system with the chemical composition (Ca, Mg, Fe) 2 Si 2 O 6 and develops short to long, prismatic crystals , but also granular mineral aggregates of green, brown or black color with a gray-green line color . Colorless Augites ( Leukaugite ) are also found very rarely .

With a Mohs hardness of 5 to 6, Augite is one of the medium-hard minerals and, like the reference mineral apatite (hardness 5), can be scratched with a knife or like the reference mineral orthoclase with a steel file.

Etymology and history

Augit was first described in 1792 by the German mineralogist Abraham Gottlob Werner and named after the Greek word αὐγή auge , which means something like shine.

classification

In the structural classification of the International Mineralogical Association (IMA) augite belongs together with Burnettit , Davisit , diopside , Essenit , Grossmanit , Hedenbergit , Johannsenite , Kushiroit , Petedunnit and Tissintit to Kalziumpyroxenen (Ca pyroxene) in pyroxene .

In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the augite belonged to the mineral class of "silicates and germanates" and there to the general department of " chain and band silicates (inosilicates) ", where it was used together with aegirine , diopside, Esseneit, Hedenbergit, Jadeit , Jervisit , Johannsenite, kanoite , clino-enstatite , Klinoferrosilit , Kosmochlor , Namansilit , Natalyit , omphacite , Petedunnit, pigeonite and spodumene the subgroup of clinopyroxene within the pyroxene formed.

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also assigns Augit to the class of "silicates and germanates" and there in the department of "chain and band silicates (inosilicates)" a. In the meantime, however, this department is more precisely subdivided according to the type of chain or band formation and the particular relationship of some minerals, so that the mineral is classified accordingly in the subdivision “Chain and band silicates with 2-periodic single chains Si 2 O 6 ; Pyroxen family "is to be found, where together with diopside, essenite, hedenbergite, johannsenite and petedunnite the" Ca-clinopyroxene, diopside group "with the system no. 9.DA.15 forms.

The systematics of minerals according to Dana also assigns Augit to the class of "silicates" and there to the department of "chain silicate minerals". There he is, also together with Diopside, Esseneit, Hedenbergite, Johannsenite and Petedunnit, a member of the group "C2 / c Klinopyroxene (Ca-Klinopyroxene)" with the system no. 65.1.3a within the subsection “ Chain Silicates : Simple unbranched chains, W = 1 with chains P = 2 ”.

Crystal structure

Augite crystallizes monoclinically in the space group C 2 / c (space group no. 15) with the lattice parameters a  = 9.69  Å ; b  = 8.84 Å; c  = 5.28 Å and β = 106.3 ° and 4 formula units per unit cell . Template: room group / 15

properties

In front of the soldering tube , augite melts into black, often magnetic glass . It is generally only weakly attacked by acids , with the exception of hydrofluoric acid .

Titanium augite, on the other hand, is completely decomposable in boiling hydrochloric acid (HCl).

Modifications and varieties

As Fassait a Augit- or diopside variety with an increased iron -, and aluminum content referred to.

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

In the Petrographie the distinction between augite and titanaugite excess (> 3 wt .-% TiO 2 ) common. This can often be recognized in the thin section without chemical analysis by its brown-violet to violet color, whereby the intensity of the color usually increases with the titanium content.

Education and Locations

Augite crystals on host rock from Diana Township, Lewis County, New York, USA

Augite is a rock-forming mineral that forms as an essential part of a mixture in many and as an accessory component in most igneous rocks such as basalts , diabase , gabbros , melaphyren and tuffs . Accompanying minerals include various minerals from the amphibole group , labradorite , leucite , olivine , orthoclase , sanidine and various minerals from the pyroxene group .

As a frequent mineral formation, Augite can be found in many localities, with over 2000 localities being known to date (as of 2017).

In Germany the mineral was found in various quarries and mines in Hegau and the Kaiserstuhl in Baden-Württemberg, in Franconia and in Lower Bavaria , in the district of Giessen and in Vogelsberg in Hesse; in various places in the Harz in Lower Saxony; in several places in the Siebengebirge and Siegerland ; in many places in the Eifel such as in the area around Andernach , Daun , Gerolstein , Hillesheim , the Laacher See , Mayen , Mendig and Niederzissen ; in the Ore Mountains in Saxony and in some places in Saarland , Schleswig-Holstein and Thuringia .

In Austria, Augit has been found in several places in Burgenland , in Carinthia (Hohe Tauern, Hüttenberger Erzberg, Koralpe), Lower Austria (Waldviertel), in Salzburger Land , Styria and North Tyrol .

In Switzerland, the mineral has so far only been found in a few places, for example on the Tot Alp near Wolfgang in Davos in the canton of Graubünden, in two outcrops in the municipality of Ramsen SH in the canton of Schaffhausen and on Allalin in the municipality of Saas-Almagell in the canton of Valais .

The site at Clear Lake in the Canadian province of Ontario , where crystals up to 15 cm in size emerged, is worth mentioning due to the extraordinary Augit finds . Crystals up to 5 cm in size were found at Lake Laacher in Rhineland-Palatinate (Germany).

Other sites are found in Egypt , Algeria , the Antarctic , Argentina , Armenia , Azerbaijan , Ethiopia , Australia , Bangladesh , Bolivia , Brazil , Bulgaria , Burkina Faso , Chile , China , Costa Rica , Ecuador , El Salvador , Eritrea , on the Fiji Island Ovalau, Finland , France as well as French Polynesia and French West Indies , Ghana , Greece , Greenland , Guatemala , Guinea , India , Indonesia , Iran , Iraq , Ireland , Iceland , Israel , Italy , Japan , Yemen , on the Virgin Islands , Cameroon , Kazakhstan , Kenya , Kyrgyzstan , Republic of the Congo , Colombia , North and South Korea , Croatia , Libya , Lithuania , Madagascar , Malawi , Mali , Malta , Morocco , Mauritania , Mauritius , Mexico , Mongolia , Montserrat , Myanmar , Namibia , New Caledonia , New Zealand , Nicaragua , the Netherlands , Nigeria , Norway , Oman , Pakistan , Papua New Guinea , Paraguay , the Philippines , Poland , Portugal , Réunion , Romania , Russia , the West Sahara , the Solomon Islands , Saudi Arabia , Sweden , Sierra Leone , Zimbabwe , Slovakia , Spain , St. Lucia , St. Vincent and the Grenadines , South Africa , Sudan , Taiwan , Tajikistan , Tanzania , the Czech Republic , Turkey , Turkmenistan , Ukraine , Hungary , Uzbekistan , the United Kingdom (Great Britain), the United States of America (USA), Vietnam , the Central African Republic and Cyprus .

In addition, augite is a component of some stone meteorites . Augite could also be detected in rock samples from the East Pacific ridge .

Outside the earth, the mineral has been found on the moon (Mare Crisium, Mare Fecunditatis and Montes Taurus) and on Mars ( Valles Marineris , Aeolis quadrangle).

As part of his mineralogical studies, Johann Wolfgang von Goethe was also interested in the large idiomorphic Augites that occur in the Bohemian volcano Vlčí hora ( Wolfsberg ). At Goethe's instigation, the chemist Johann Wolfgang Döbereiner carried out melting tests on these Augites. Likewise were of Frédéric Soret the augites of Wolfsberg examined morphologically and published the results in a statement issued by Goethe magazine.

See also

literature

Web links

Commons : Augit  - collection of images, videos and audio files
Wiktionary: Augit  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. a b c d Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  620 .
  2. a b IMA / CNMNC List of Mineral Names; September 2017 (PDF 1.67 MB; p. 15)
  3. Webmineral - Augite (English)
  4. a b c d Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p.  526-527 .
  5. a b c Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp.  770-772 .
  6. a b c d Augite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 78  kB ; accessed on December 3, 2017]).
  7. a b c d e Mindat - Augite (English)
  8. a b Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp.  719 (first edition: 1891).
  9. Subcommite on Pyroxenes, CNMMN; Nobuo Morimoto: Nomenclature of Pyroxenes . In: The Canadian Mineralogist . tape 27 , 1989, pp. 143–156 ( mineralogicalassociation.ca [PDF; 1.6 MB ; accessed on November 11, 2018]).
  10. Old mineral names and synonyms at indra-g.at (PDF 2.65 MB; p. 81)
  11. H. Pichler, C. Schmitt-Riegraf: Rock -forming minerals in thin sections . 2nd Edition. Enke, Stuttgart 1993, p. 91-92 .
  12. Mindat - Number of locations for Augite (English)
  13. Petr Korbel, Milan Novák: Mineral Encyclopedia (=  Dörfler Natur ). Nebel Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 233 .
  14. Find location list for Augit in the Mineralienatlas and Mindat
  15. ^ Johannes Baier: Goethe and the Wolfsberg (Vlčí hora; Czech Republic) . In: Journal of Geological Sciences . tape 41/42, 2013/14 , No. 4. Verlag für Geoswissenschaften , ISSN  0303-4534 , p. 209–216 ( summary available online at zgw-online.de [PDF; 182 kB ; accessed on December 3, 2017], year of publication probably 2014).