Uvarowit

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Uvarowit
Uvarovite-uvarclose.jpg
Uvarowit from the Saranowski mine near Sarany (Сараны), Perm region , Russia ( total size of the step: 18.3 × 13.1 × 2.0 cm)
General and classification
chemical formula Ca 3 Cr 2 [SiO 4 ] 3
Mineral class
(and possibly department) 		Silicates, germanates - island silicates (nesosilicates) - garnet group
System no. to Strunz
and to Dana 		9.AD.25 ( 8th edition : VIII / A.08)
51.04.03b.03
Similar minerals Dioptase
Crystallographic Data
Crystal system cubic
Crystal class ; symbol cubic hexakisoctahedral; 4 / m  3  2 / m
Space group Ia 3 d (No. 230)Template: room group / 230
Lattice parameters a  = synthetic: 11.996  Å
Formula units Z  = 8
Physical Properties
Mohs hardness 6.5 to 7
Density (g / cm 3 ) natural: 3.77 to 3.81; synthetic: 3.5952 (calculated)
Cleavage no
Break ; Tenacity shell-like to uneven
colour emerald green to dark green
Line color White
transparency transparent to translucent
shine Glass gloss
Crystal optics
Refractive index n  = 1.865
Birefringence none, occasionally abnormally birefringent

The mineral uwarowite is a rarely occurring island silicate from the garnet group with the chemical composition Ca 3 Cr 2 [SiO 4 ] 3 . Uvarowite crystallizes in the cubic crystal system and develops mostly small, well to perfectly formed crystals , but also granular aggregates . Due to the formation of mixed crystals and foreign admixtures , the color varies from dark to emerald to brown-green. Depending on the purity, crystal defects and / or the amount of inclusions , the crystals can be glass- to fat-shiny and transparent to opaque.

Etymology and history

During his stay in St. Petersburg, the Swiss-Russian chemist and mineralogist Germain Henri Hess examined a " Dioptas von Bissersk " from the local collection, which he had requested for comparison purposes . The occurrence of a copper mineral on a chrome ore prompted him to conduct a more detailed investigation, in the course of which the supposed dioptase turned out to be a new garnet containing chromium. He named the new mineral from the deposit Biserskoje (Biser) in the Middle Urals after the Russian count, mineral collectors and President of the Imperial Academy of Sciences Sergey Uvarov Uwarowit.

Georg Menzer clarified the crystal structure in 1929 and FA Hummel succeeded in 1950 at the Pennsylvania State University in 1950 with the first synthesis of pure uwarowite .

classification

The structural classification of the International Mineralogical Association (IMA) is one of the Uwarowit to Garnet supergroup, where he along with almandine , Andradite , Calderit , Eringait , Goldmanit , Grossular , Knorringit , majorite , Menzerit- (Y) , Momoiit , Morimotoit , pyrope , Rubinite and Spessartine form the garnet group with 12 positive charges on the tetrahedrally coordinated lattice position.

Already in the outdated, but partly still in use 8th edition of the mineral systematics according to Strunz , the uwarowite belonged to the mineral class of "silicates and germanates" and there to the department of "island silicates (nesosilicates)", where it together with andradite, goldmanite and grossular the " Ugrandit series "within the" garnet group "with the system no. VIII / A.08 .

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), assigns Uwarowit to the class of “silicates and germanates” and there to the “island silicates (nesosilicates)” section. This section is further subdivided according to the possible presence of further anions and the coordination of the cations involved , so that the mineral is classified according to its composition and structure in the sub-section “Island silicates without further anions; Cations can be found in oktahedraler [6] and usually greater coordination, "where it along with almandine, Andradite, Calderit, Goldmanit, Grossular, Henritermierit , Holtstamit , katoite , Kimzeyit , Knorringit, majorite, Momoiit, Morimotoit, pyrope, Schorlomit and Spessartin the "garnet group" with the system no. 9.AD.25 forms. The garnet compounds blythite, hibschite, hydroandradite and skiagite, which are no longer regarded as minerals, were also included in this group. Wadalite , at that time still grouped with the grenades, proved to be structurally different and is now assigned to a separate group with chloromayenite and fluoromayenite . The garnets irinarassite , hutcheonite , kerimasite , toturite , menzerite (Y) and eringaite described after 2001 would have been classified in the garnet group.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Uvarowit to the class of "silicates and Germanates" and there in the department of "island silicate minerals ". Here it is together with andradite, grossular, goldmanite and yamatoite (discredited because it is identical to momoiite) in the "garnet group (Ugrandite series)" with the system no. 51.04.03b to be found within the subsection of " Island silicates: SiO 4 groups only with cations in [6] and> [6] coordination ".

composition

Uvarowite with the idealized composition [X] Ca 2+ 3 [Y] Cr 3+ [Z] Si 3 O 12 is the chromium analog of grossular ( [X] Ca 2+ 3 [Y] Al [Z] Si 3 O) 12 ) and occurs in nature always as mixed crystal with grossular and andradite. There is unlimited miscibility with both end members, depending on the exchange reactions

  • [Y] Cr 3+ = [Y] Al 3+ , (grossular),
  • [Y] Cr 3+ = [Y] Fe 3+ , (andradite)

On the dodecahedral X position, Ca 2+ can be replaced by Mg 2+ , according to the exchange reactions

  • [X] Ca 2+ = [X] Mg 2+ (knorringite),
  • [X] Ca 2+ + [Y] Cr 3+ = [X] Mg 2+ + [Y] Al 3+ (pyrope)

The Fe 2+ and Mn 2+ contents are consistently low.

In contrast to grossular and andradite, no OH-rich Uwarowites have been described so far.

Crystal structure

Uwarowit crystallizes in the cubic system in the space group Ia 3 d (space group no. 230) with the lattice parameter a  = 12.00  Å and eight formula units per unit cell . Template: room group / 230

The structure is that of garnet . Calcium (Ca 2+ ) occupies the dodecahedral X positions surrounded by 8 oxygen ions, chromium (Cr 3+ ) the octahedral Y position surrounded by 6 oxygen ions and the tetrahedral Z position surrounded by 4 oxygen ions is exclusively silicon (Si 4+ ) occupied.

Like many calcium grenades, natural uwarowites are occasionally slightly birefringent , which is usually taken as an indication of a lower, non-cubic symmetry. Recent studies with high resolution synchrotron - X-ray diffraction showed that at least the tested birefringent Uwarowite mixtures of two or three in each cubic shells of different composition and slightly different lattice parameters are. This intergrowth of shells with different lattice constants leads to lattice stresses which cause birefringence.

properties

Natural uwarowites are always mixed crystals, the physical properties of which vary with the composition. For example, the Mohs hardness scale for Uwarowit ranges from 6.5 to 7 (according to other sources 7 to 7.5) and the density from 3.4 to 3.8 g / cm³.

The color shows a more complex dependence on the composition of the uvarovite solid solution. With increasing chromium content (Cr 3+ ), the intensity of the green color increases. With increasing replacement of calcium (Ca 2+ ) by magnesium (Mg 2+ ) in the X position, the color changes from green to gray to deep purple-red, at least in the case of grossular-rich Uvarowites. The color change with increasing Mg contents is accompanied by a decrease in the covalent portion of the chromium-oxygen bond. The bond length remains almost unchanged.

A similar effect is also produced by changing the pressure. On a natural uvarowite, a change in color from green (0.0001 GPa) through gray (8 GPa) to red (13 GPa) was observed with increasing pressure. In contrast to the color change in mixed crystals, the character of the bond does not change here, but the bond length.

Education and Locations

Uvarowite on quartz from the Outokumpu ore field, Eastern Finland . Size of the uvarowite crystal 1.2 cm

Uvarowite is mainly formed in metamorphic or hydrothermal contexts, less often in igneous rocks such as pegmatite . In order to develop , the mineral needs increased chromium content and an ultra- basic environment, i.e. a particularly low content of silicon dioxide (SiO 2 ). These conditions can be found in chromite-containing serpentinites and skarns .

The most famous sites in Russia are the mines in the Perm region near Biser in the south of Saranovskoye and Teplaja Gora near Sarany , where uvarovite crystals of up to eight millimeters have been found. In Sverdlovsk Oblast , Verch-Nejvinskij , Alapaewsk , Stary Itkul'skoje and Iremel'skoye should be mentioned.

Crystals of up to two centimeters and particularly large crystal aggregates come from the Finnish Outokumpu deposit .

Other sites include Assosa in the Woolga Province in Ethiopia ; the chromite deposits in southeastern New South Wales and Tasmania in Australia ; Xinjiang in the People's Republic of China ; Mokkivaara and Pohjois-Karjala in Finland ; the Lombardy and Val Malenco in Italy ; the prefectures of Kōchi and Ehime in Japan ; Québec in Canada ; in the Moa Baracoa massif, as deposits in the serpentinite in the province of Guantánamo in Cuba ; Nordland , Røros , Grua and Velfjord in Norway ; Styria and Tyrol in Austria ; in the serpentinite massif of the region around Sobótka in Poland ; Eastern Anatolia and Cape Dağları in Turkey ; as well as Alaska , Arizona , various regions in California , Colorado , Maine , Michigan , Nevada , New Mexico , New York , Oregon , Pennsylvania , Texas , Vermont and Washington in the USA .

Use as a gem stone

Uvarowit followers

Uvarowit is mainly processed into gemstones . Pieces of jewelery in which uvarowit has been processed can be traced back to the Merovingian era.

The first scientific description of Uvarowit is based on its occurrence in the Urals. The best crystals from this deposit were used to manufacture precious stones at the imperial court. In Russian history one speaks of the "imperial stone" because the inclination of Tsarina Catherine II for this mineral is known.

Uvarowite is sometimes confused with the equally rare and somewhat lighter green andradite variety demantoid (Fe 3+ Cr 3+ ). Another color possibility of confusion exists with the Grossular -Varietät tsavorite and with emerald and Dioptas .

See also

literature

Monographs
  • Takeo Bamba, Kenzo Yagi, Kenjiro Maed: Chrome Garnet from the Vicinity of Nukabira Mine, Hidaka Province, Hokkaido, Japan . In: Proceedings of the Japan Academy . tape 45 , no. 2 , 1969, p. 109–114 ( jst.go.jp [PDF; 1.5 MB ; accessed on April 30, 2017]).
  • RJ Ford: A hydro garnet from Tasmania . In: Mineralogical Magazine . tape 37 , no. 292 , December 1970, p. 942–943 ( rruff.info [PDF; 99 kB ; accessed on April 30, 2017]).
  • Ian T. Graham, M. David Colchester: The Occurrence and Origin of Well-crystallized Uvarovite Garnet from the Podiform Chromitite Deposits of South-eastern New South Wales . In: Journal and Proceedings of The Royal Society of New South Wales . tape 128 , no. 3-4 , 1995, pp. 79-88 ( available online at biodiversitylibrary.org [accessed April 30, 2017]).
Compendia
  • 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. 460 ff .
  • Petr Korbel, Milan Novák: Mineral Encyclopedia (=  Villager Nature ). Nebel Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 199 .
  • 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. 83 ff .

Web links

Commons : Uwarowit (Uvarovite)  - collection of images, videos and audio files
Wikisource: Ueber den Kalkchromgranat  - Sources and full texts
Wiktionary: Uwarowit  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ^ A b 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.  541 .
  2. ↑ Webmineral - Uvarovite (English)
  3. ↑ a b c d HG Huckenholz, D. Knittel: Uvarovite: Stability of uvarovite-grossularite solid solution at low pressure . In: Contributions to Mineralogy and Petrology . tape 49 , 1975, pp. 211-232 , doi : 10.1007 / BF00376589 .
  4. ↑ a b c DK Teertstra: Index-of-refraction and unit-cell constraints on cation valence and pattern of order in garnet-group minerals . In: The Canadian Mineralogist . tape 44 , 2006, pp. 341–346 ( rruff.info [PDF; 197 kB ; accessed on May 5, 2018]).
  5. ↑ a b c d e Uvarovite . 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; 67  kB ; accessed on April 30, 2017]).
  6. ↑ a b Oleg von Knorring: A new occurrence of uvarovite from northern Karelia in Finland. In: Mineralogical Magazine . tape 29 , 1951, pp. 594–601 ( minersoc.org [PDF; 2.8 MB ; accessed on May 11, 2018]).
  7. ↑ a b Michael Andrut and Manfred Wildner: spectroscopy absorption Part I. Optical investigations and UV-VIS-IR: The crystal chemistry of natural birefringent uvarovites . In: The American Mineralogist . tape 86 , 2001, p. 1219–1230 ( minsocam.org [PDF; 39 kB ; accessed on May 12, 2018]).
  8. ↑ a b Manfred Wildner and Michael Andrut: The crystal chemistry of birefringent natural uvarovites: Part II. Single-crystal X-ray structures . In: The American Mineralogist . tape 86 , 2001, p. 1231–1251 ( minsocam.org [PDF; 46 kB ; accessed on May 12, 2018]).
  9. ↑ a b Jeffrey Juan Salvador: Crystal Chemistry and Structure of Anomalous Birefringent Cubic Uvarovite Garnet, Ideally Ca3 Cr2 Si3 O12 . In: GRADUATE PROGRAM IN GEOLOGY AND GEOPHYSICS . 2017 ( ucalgary.ca [PDF; 20.0 MB ; accessed on May 12, 2018]).
  10. ^ A b c Edward S. Grew, Andrew J. Locock, Stuart J. Mills, Irina O. Galuskina, Evgeny V. Galuskin and Ulf Hålenius: IMA Report - Nomenclature of the garnet supergroup . In: The American Mineralogist . tape 98 , 2013, p. 785–811 ( main.jp [PDF; 2,3 MB ; accessed on July 8, 2017]).
  11. ↑ H. Hess: Ueber den Uwarowit, a new mineral species . In: Annals of Physics and Chemistry . tape 24 , 1832, pp. 388–389 ( rruff.info [PDF; 132 kB ; accessed on May 15, 2018]).
  12. ↑ a b c G. Menzer: The crystal structure of the grenade . In: Journal of Crystallography - Crystalline Materials . tape 69 , 1929, pp. 300-396 , doi : 10.1524 / zkri.1929.69.1.300 .
  13. ^ FA Hummel: Synthesis of Uvarovite . In: American Mineralogist . tape 35 , no. 3–4 , 1950, pp. 324-325 ( minsocam.org [PDF; 219 kB ; accessed on April 30, 2017]).
  14. ^ A b T. Isaacs: A study of uvarovite . In: Mineralogical Magazine . tape 35 , 1965, pp. 341–346 ( minersoc.org [PDF; 328 kB ; accessed on May 11, 2018]).
  15. ^ Joaquín Proenza, Jesús Solé, Joan Carles Melgarejo: Uvarovite in podiform chromitite: the Moa-Baracoa ophiolitic massif, Cuba . In: The Canadian Mineralogist . tape 37 , 1999, pp. 679-690 ( rruff.info [PDF; 3.3 MB ; accessed on April 30, 2017]).
  16. ^ HG Huckenholz, D. Knittel: Uvarovite: Stability of uvarovite-andradite solid solutions at low pressure . In: Contributions to Mineralogy and Petrology . tape 56 , 1976, pp. 61-76 , doi : 10.1007 / BF00375421 .
  17. ↑ Tapan Pal and Dipankar Das: Uvarovite from chromite-bearing ultramafic intrusives, Orissa, India, a crystal-chemical characterization using 57Fe Mössbauer spectroscopy . In: The American Mineralogist . tape 95 , 2010, p. 839–843 ( minsocam.org [PDF; 342 kB ; accessed on May 12, 2018]).
  18. ↑ Biswajit Ghosh and Tomoaki Morishita: ANDRADITE-UVAROVITE SOLID SOLUTION FROM HYDROTHERMALLY ALTERED PODIFORM CHROMITITE, RUTLAND OPHIOLITE, ANDAMAN, INDIA . In: The Canadian Mineralogist . tape 49 , 2011, p. 573-580 , doi : 10.3749 / canmin.49.2.573 .
  19. ↑ a b Alexei N. Platonov, Klaus Langer, Stanislav S. Matsyuk: Crystal field and covalency of octahedral chromium in natural [8] (Mg1 - x Ca x) 3 [6] (Al0.67Cr0.33) 2Si3O12 garnets from upper mantle rocks . In: Physics and Chemistry of Minerals . tape 35 , no. 6 , 2008, p. 331-337 , doi : 10.1007 / s00269-008-0226-6 .
  20. ↑ KL Chakraborty: Mineralogical note on the chrome-chlorite (kämmererite) and chrome-garnet (uvarovite) from the chromite deposits of Kalrangi, Orissa, India . In: Mineralogical Magazine . 1968 ( minersoc.org [PDF; 183 kB ; accessed on May 12, 2018]).
  21. ^ A b GA Novak and GV Gibbs: The crystal chemistry of the silicate garnets . In: The American Mineralogist . tape 56 , 1971, p. 791–825 ( rruff.info [PDF; 2,3 MB ; accessed on May 4, 2018]).
  22. ↑ Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 6th completely revised and supplemented edition. Weise, Munich 2014, ISBN 978-3-921656-80-8 .
  23. ^ MN Taran, K. Langer and M. Koch-Müller: Pressure dependence of color of natural uvarovite: the barochromic effect. In: Physics and Chemistry of Minerals . tape 35 , no. 6 , 2008, p. 175–177 ( gfz-potsdam.de [PDF; 960 kB ; accessed on May 13, 2018]).
  24. ↑ Find location list for Uwarowit at the Mineralienatlas and at Mindat
  25. ↑ Dieter Quast, Ulrich Schüßler: Mineralogical investigations on the origin of the garnet from Merovingian cloisonné work . In: Germania . tape 78 , 2000, ISSN  0016-8874 , p. 75-96 .