Diopside

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Diopside
Diopside-225169.jpg
Diopside from De Kalb Township, St Lawrence County, New York , USA
Size: 4.3 × 3.3 × 1.9 cm
General and classification
chemical formula CaMg [Si 2 O 6 ]
Mineral class
(and possibly department) 		Chain and band silicates ; Clinopyroxene group
System no. to Strunz
and to Dana 		9.DA.15 ( 8th edition : VIII / F.01)
65.01.03a.01
Similar minerals Augit
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  = 9.75  Å ; b  = 8.92 Å; c  = 5.25 Å
β  = 106.0 °
Formula units Z  = 4
Frequent crystal faces {100}, {010}, {111}, { 1 11}, {110}, {310}, { 3 31}, {001}, {10 1 }
Twinning simple and multiple twins according to {100} or {010}
Physical Properties
Mohs hardness 5.5 to 6.5
( HV : 7.7 ± 0.5 GPa at 0.98 N)
Density (g / cm 3 ) measured: 3.22 to 3.38; calculated: 3.278
Cleavage clearly after {110}
Break ; Tenacity uneven to scalloped
colour colorless, white, yellow, light to dark green, black
Line color White
transparency transparent to opaque
shine Glass gloss, fat gloss, matt
Crystal optics
Refractive indices n α  = 1.663 to 1.699
n β  = 1.671 to 1.705
n γ  = 1.693 to 1.728
Birefringence δ = 0.030
Optical character biaxial positive
Axis angle 2V = 58 ° to 63 ° (measured), 56 ° to 64 ° (calculated)
Pleochroism blue-green-green-brown-yellow-green
Other properties
Chemical behavior Almost insensitive to acids (exception: hydrofluoric acid )

Diopside is a very common mineral from the mineral class of " silicates and germanates ". It crystallizes in the monoclinic crystal system with the composition CaMg [Si 2 O 6 ], so it is chemically a calcium - magnesium silicate and structurally belongs to the chain silicates and there to the group of pyroxenes .

Diopside develops short to long, prismatic crystals , but is also found in the form of columnar, lamellar or granular mineral aggregates . In its pure form it is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline training, it can also appear white and, due to foreign admixtures, take on a yellow, light to dark green or black color, the transparency decreasing accordingly to the point of opacity.

Diopside, together with hedenbergite CaFe [Si 2 O 6 ] and augite (Ca, Na) (Mg, Fe, Al) [(Si, Al) 2 O 6 ], forms a complete mixed series .

Etymology and history

The name Diopside comes from the Greek δίς dis for double, ὄψις opsis for sight and εἶδος eidos for shape and indicates that the diopside crystals often appear as twins .

The mineral was first described in 1800 by José Bonifácio de Andrada e Silva , albeit under the name coccolite . He gave the Hellesta and Åssebro iron mines in the Swedish Södermanland as sites . However, it was later proven that de Andrada's mineral is identical to the diopside described by René-Just Haüy in 1806, and the name Coccolite was discredited.

classification

In the structural classification of the International Mineralogical Association (IMA) diopside belongs together with pyroxene , Burnettit , Davisit , 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 diopside belonged to the mineral class of "silicates and germanates" and there to the department of "chain silicates and band silicates (inosilicates)", where it together with Aegirin , Augit, Esseneit, Hedenbergit, Jadeit , Jervisit , Johannsenite, kanoite , clino-enstatite , Klinoferrosilit , Kosmochlor , Namansilit , Natalyit , omphacite , Petedunnit, pigeonite and spodumene the "pyroxene group, subgroup clinopyroxene" with the system number. VIII / F.01 .

The 9th edition of Strunz's mineral systematics , which has been in force since 2001 and is used by the International Mineralogical Association (IMA), also assigns the diopside to the class of "silicates and germanates" and there in the department of "chain and band silicates (inosilicates)" a. However, this department is further subdivided according to the type of chain formation, so that the mineral is classified in the subdivision “Chain and band silicates with 2-periodic single chains Si2O6; Pyroxene family "can be found, where together with Augite, Esseneit, Hedenbergite, Johannsenite and Petedunnit the" Ca-Klinopyroxene, diopside group "with the system no. 9.DA.15 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the diopside to the class of "silicates and Germanates" and there in the department of "chain silicate minerals". Here it is together with hedenbergite, augite, johannsenite, petedunnite, esseneit and davisite in the group of " C 2 / c clinopyroxene (Ca-clinopyroxene)" with the system no. 65.01.03a can be found in the subsection " Chain Silicates: Simple unbranched chains, W = 1 with chains P = 2 ".

Crystal structure

Diopside crystallizes monoclinically in the space group C 2 / c (space group no. 15) with the lattice parameters a  = 9.75  Å ; b  = 8.92 Å; c  = 5.25 Å and β = 106.0 ° and 4 formula units per unit cell . Template: room group / 15

Modifications and variations

  • Chromium diopside - containing chromium, emerald green
  • Baikalite - ferrous, leek green to olive green
  • Diallag - contains aluminum and iron, green-brown to brown-black, pearlescent, rock-forming
  • Fassait - containing iron and aluminum
  • Fedorovite - containing sodium, aluminum and iron, light green from the province of Rome
  • Jeffersonite - containing manganese and zinc
  • Salit - greenish-gray, rock-forming

Education and Locations

Pyrite, grossular, and diopside from Belvidere Mountain Quarry, Vermont, USA

Diopside is a rock- forming mineral found in basic and ultra- basic rocks such as gabbro and peridotite . As Begleitminerale occur among other calcite , Chondrodite , forsterite , Grossular , Klinohumit , Monticellite , quartz , scapolite , tremolite , Vesuvianit and wollastonite on.

Diopside has already been found at many sites around the world, with around 2900 known to date (as of 2012).

In Germany the mineral occurred among other things in several places in the Black Forest , the Odenwald and at the Kaiserstuhl in Baden-Württemberg; in the Fichtelgebirge , in the Bavarian and Upper Palatinate Forest in Bavaria; near Giesel (Neuhof) , Hochstädten (Bensheim) and Nieder-Ramstadt in Hesse; near Güntersen and Bad Harzburg in Lower Saxony; on the Finkenberg and on the Dächelsberg near Niederbachem in North Rhine-Westphalia; in many places in the Eifel in Rhineland-Palatinate; in the Ore Mountains in Saxony; near Damsdorf in Schleswig-Holstein as well as near Ronneburg , Schnellbach (Floh-Seligenthal) and at Dolmar in Thuringia.

In Austria, diopside has so far been found mainly in Carinthia , Lower Austria , Salzburg , Styria and Tyrol .

In Switzerland, the mineral occurs mainly in the cantons of Graubünden and Valais .

Diopside could also be detected in rock samples from the Mid-Atlantic Ridge and the East Pacific Ridge .

Diopside in gemstone quality are in Brazil , Burma , on Madagascar and Sri Lanka found.

Outside the earth, diopside has also been found, namely in rock samples from the moon , from Noctis Labyrinthus on Mars and in the comet dust from Wild 2 .

Use as a gem stone

Diopside in the form of a turnip sanded

Gem-quality diopside are processed into gemstones . This includes above all the Russian chromium diopside.

See also

literature

  • JB d'Andrada : Brief description of the properties and characteristics of some new fossils from Sweden and Norway, along with some chemical remarks about them . In: D. Alexander Nicolaus Scherer (Ed.): General Journal of Chemistry . 1800, Volume 4, pp. 28-39 ( PDF 2.36 MB ; p. As Coccolit).
  • M. Haüy : Sur L'Analogie du Diopside avec le Pyroxène . In: Annales du Muséum d'histoire naturelle. 1808, Volume 11, p. 77 ( full text in the Google book search).
  • Martin Okrusch, Siegfried Matthes: Mineralogy. An introduction to special mineralogy, petrology and geology . 7th fully revised and updated edition. Springer Verlag, Berlin et al. 2005, ISBN 3-540-23812-3 , pp. 94 .
  • Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp. 717–718 (first edition: 1891).
  • Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 232 ( Dörfler Natur ).

Web links

Commons : Diopside  - collection of pictures, videos and audio files

Individual evidence

  1. ↑ Webmineral - Diopside
  2. ^ A b c Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  620 .
  3. ^ Helmut Schrätze, Karl-Ludwig Weiner: Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 758 .
  4. ↑ a b c d e John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols: Diopside . In: Handbook of Mineralogy, Mineralogical Society of America . 2001 ( PDF 77.2 kB ).
  5. ↑ corresponds to 785 ± 51 HV 0.1
  6. ↑ M., M Smedskjaer, M. Jensen, Y.-Z. Yue: Theoretical calculation and measurement of the hardness of diopside . In: Journal of the American Ceramic Society . 91, 2008, pp. 514-518.
  7. ↑ a b c d Mindat - Diopside
  8. ^ Mindat - Coccolite
  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. ↑ a b c Mindat - Localities for Diopside