Eltyubyuit

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Eltyubyuit
General and classification
other names

IMA 2011-022

chemical formula Ca 12 Fe 10 3+ Si 4 O 32 Cl 6
Mineral class
(and possibly department) 		Silicates and Germanates
System no. according to Strunz 9.AD.25 ( 8th edition : VIII / A.08)
Similar minerals Wadalite , andradite
Crystallographic Data
Crystal system cubic
Crystal class ; symbol cubic-hexakistrahedral; 4  3  m
Space group I 4 3 d (No. 220)Template: room group / 220
Lattice parameters a  = natural: 12.2150  Å
Formula units Z  = 2
Frequent crystal faces Triakis tetrahedron {211},
Physical Properties
Mohs hardness Please complete!
Density (g / cm 3 ) calculated: 3.349
Cleavage Please complete!
colour light brown to yellow
Line color Please complete!
transparency Please complete!
shine Please complete!
Crystal optics
Refractive index n  = 1.85
Birefringence no

The mineral Eltyubyuit is a very rarely occurring island silicate from the mayenite upper group with the idealized chemical composition Ca 12 Fe 3+ 10 Si 4 O 32 Cl 6 . It crystallizes in the cubic crystal system with the structure of chloromayenite .

Eltyubyuit is transparent to translucent and only develops small, lime-yellow to light brown crystals less than one mm in size. The crystal form is dominated by the triakis tetrahedron {211}.

Eltyubyuit is formed in contact metamorphic form at low pressure and very high temperatures during the sanidinite facial conversion of rocks rich in calcium and aluminum by fluids rich in chlorine and is found in skarn inclusions in igneous rocks .

Etymology and history

Eltyubyu village in Chegem district, after which the mineral is named.

A cubic calcium aluminate has been known since the beginning of the 20th century, for which the composition 5CaO · 3Al 2 O 3 was given at the time. Since calcium aluminates are important compounds in cement clinker, they have been intensively studied since then.

The structure of this compound was elucidated in 1936 by W. Büssem and A. Eitel at the Kaiser Wilhelm Institute for Silicate Research in Berlin-Dahlem . In the course of the structure determination, they corrected the composition to 12CaO · 7Al 2 O 3 .

The aluminum analog of Eltyubyuit, a chlorosilicate with the structure of 12CaO 7Al 2 O 3 determined by Büssem and Eitel , was discovered in 1993 by Tsukimura and co-workers in a skarn xenolite of an andesite near Tadano near Kōriyama in Fukushima Prefecture , Japan . They described the structure in analogy to the garnet structure and wadalite was therefore long assigned to the garnet group .

In 1995, Glasser once again highlighted the differences between the structures of wadalite and garnet and current classifications classify garnet and wadalite in different mineral groups .

In 2010 Mihajlovic and co-workers described an iron-rich wadalite from a carbonate xenolite from the leucite - tephrite , which is mined in the quarry of the company "A. Caspar" on the Bellerberg volcano near Mayen in the Vulkaneifel in Rhineland-Palatinate , Germany .

Three years later, Eltyubyuit was discovered in a carbonate xenolite from the Ignimbrites of the Chegem Caldera in the North Caucasian Republic of Kabardino-Balkaria in Russia . Eltyubyuit was named after the nearby village of Eltyubyu.

In 2015, finally, nearly pure, aluminum-free Eltyubyuit in a carbonate-silicate xenoliths from was dacite of Shadil-Khokh volcano , Kel 'Plateau in Southern Ossetia , Georgia found.

Meanwhile, from 2010 to 2014, further minerals of the mayenite upper group were found and the group and mineral definitions were revised by EV Galuskina and colleagues.

classification

The current classification of the International Mineralogical Association (IMA) counts the Eltyubyuit to the mayenite upper group , where together with its Al 3+ analogs wadalite and adrianite it forms the wadalite group with more than 4 Cl and 2 Si per formula unit.

The outdated, but still in use 8th edition of the mineral classification according to Strunz does not list the Eltyubyuit. As an iron analogue of wadalite it would be part of the "garnet group" with the system no. VIII / A.08 in the department of " island silicates (nesosilicates)".

The 9th edition of Strunz's mineral systematics, which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), does not yet know the Eltyubyuit either. Here it would also be in the "garnet group" with the system no. 9.AD.25 belong to the department of "Island Silicates (Nesosilicates)".

The systematics of minerals according to Dana , which is mainly used in the English-speaking area , does not yet list the Eltyubyuit. Together with Wadalit he would be assigned to the unnamed group 51.04.05 of the department of " Island Silicate Minerals ".

Chemism

Eltyubyuit with the idealized composition [X] Ca 12 [T] (Fe 3+ 10 Si 4 ) O 32 [W] Cl 6 is the iron analogue of wadalite ( [X] Ca 12 [T] (Al 3+ 10 Si 4 ) O 32 [W] Cl 6 ) with which it forms mixed crystals according to the exchange reaction

  • [T] Fe 3+ = [T] Al 3+ (wadalite)

where [X], [T] and [W] are the positions in the mayenite structure.

The composition from the type locality is

  • [X] (Ca 12.12 ) [T] (Mg 0.04 Ti 0.11 Al 1.26 Fe 3+ 9.41 Si 2.98 ) O 31.89 [W] [Cl 5.94 ]

In addition to the mixed crystal formation with wadalite, further exchange reactions lead to deviations of the composition from the ideal end link composition of the Eltyubyuit. The composition shifts in the direction of the Fe analog of chloromayenite according to the exchange reaction

  • [T] Si 4+ + [W] Cl - = [T] Fe 3+ + [W] □. (Chlormayenit-Fe),

Low magnesium contents indicate mixed crystal formation with the Mg-Si analogue adrianite ( [X] Ca 12 [T] (Mg 5 2+ Si 4+ 9 ) O 32 [W] Cl - 6 ) according to the exchange reaction

  • 2 [T] Al 3+ = [T] Mg 2+ + [T] Si 4+

Crystal structure

Eltyubyuit crystallizes with cubic symmetry in the space group I 4 3 d (space group no. 220) with 2 formula units per unit cell . The natural mixed crystal from the type locality has the lattice parameter a  = 12.20  Å . For aluminum-free Eltyubyuit, a  = 12.2510 Å was measured. Template: room group / 220

The structure is that of chlormayenite . Iron (Fe 3+ ) and silicon (Si 4+ ) occupy the two Z-positions surrounded by 4 oxygen ions in a tetrahedral manner . They form a tetrahedral structure that encloses interconnected cages. Each of these cages is filled with two calcium (Ca 2+ ) ions, which are irregularly surrounded by 6 oxygen. The cages contain a chlorine ion (Cl - ) in their center between the calcium ions .

Education and Locations

Eltyubyuit forms at low pressure and high temperatures in the presence of fluids containing chlorine, generally in skarns during contact metamorphosis of calcium-rich sediments . Silicates such as chlorine Rusinovit and Rondorfit then formed instead of Rank Init and bredigite and minerals of the mayenite upper group instead of garnet , z. B. Eltyubyuit instead of andradite or wadalite instead of grossular .

The type locality of Eltyubyuit is a contact metamorphic carbonate-silicate xenolite from an ignimbrite of the Chegem Caldera in the North Caucasian Republic of Kabardino-Balkaria in Russia . Begleitminerale are Hydroxylellestadit , Edgrewit - Hydroxyledgrewit , Chegemit - Fluorchegemit , Cuspidin , Lakargiit , perovskite , Kerimasit , Srebrodolskit and Dovyrenit .

In a kontaktmetamorphen carbonate silicate Xenoliths from a dacite of Shadil-Khokh volcano , Kel 'plateau in southern Ossetien , Georgia occurs Eltyubyuit in contact with Rusinovit, cuspidine Rondorfit and hydrocalumite on. More Begleitminerale are spurrite , Larnite , gehlenite , merwinite , bredigite, Srebrodolskit, wollastonite , wadalite, Magnesioferrit and Ti-containing Andradite.

In xenoliths of leucite - Tephrits from Bellerberg volcano in Mayen in the Eifel in Rhineland-Palatinate , Germany , iron-rich wadalite occurs (no Eltyubyuit) together with gehlenite, Cuspidin, ellestadite , fluorite , ettringite , gypsum and Reinhardbraunsit on.


Web links

Individual evidence

  1. ↑ a b c d e f g h i j k l m n Evgeny V. Galuskin, Irina O. Galuskina, Radu Bailau, Krystian Prusik, Viktor M. Gazeev, Aleksandr E. Zadov, Nikolai N. Pertsev, Lidia Jeżak, Anatoly G. Gurbanov, Leonid Dubrovinsky: Eltyubyuite, Ca12Fe3 + 10Si4O32Cl6 - the Fe3 + analogue of wadalite: a new mineral from the Northern Caucasus, Kabardino-Balkaria, Russia . In: European Journal of Mineralogy . tape 25 , 2013, p. 221-229 , doi : 10.1127 / 0935-1221 / 2013 / 0025-2285 .
  2. ↑ a b c d e f g h i j k l m Frank Gfeller, Dorotas Rodek, Joachim Kusz, Mateusz Dulski, Viktor Gazeev, Irina Galuskina, Evgeny Galuskin, Thomas Armbruster: Mayenite supergroup, part IV: Crystal structure and Raman investigation of Al-free eltyubyuite from the Shadil-Khokh volcano, Kel 'Plateau, Southern Ossetia, Russia . In: European Journal of Mineralogy . tape 27 , 2015, p. 137-143 ( psu.edu [PDF; 333 kB ; accessed on July 26, 2018]).
  3. ↑ Mindat - Wadalit
  4. ^ Ernest Stanley Shepherd, GS Rankin: The binary systems of alumina with silica, lime, and magnesia; with optical study by Fred. Eugene Wright . In: American Journal of Science . tape 28 , 1909, pp. 293-333 , doi : 10.2475 / ajs.s4-28.166.293 .
  5. ↑ a b W. Büssem, A. Eitel: The structure of Pentacalciumtrialuminats . In: Journal of Crystallography . tape 95 , 1936, pp. 175–188 ( rruff.info [PDF; 628 kB ; accessed on July 22, 2018]).
  6. ↑ K. Tsukimura, Y. Kanazawa, M. Aoki, M. Bunno: Structure of wadalite Ca6Al5Si2O16Cl3 . In: Acta Crystallographica Section C . C49, 1993, pp. 205-207 , doi : 10.1107 / S0108270192005481 .
  7. ↑ FP Glasser: Comments on wadalite, Ca6AIsSiO16CI3, and the structures of garnet, mayenite and calcium chlorosilicate. Addendum. In: Acta Crystallographica Section C . tape 51 , 1995, p. 340 ( wiley.com [PDF; 108 kB ; accessed on June 30, 2018]).
  8. ↑ a b c d Tamara Mihajlovic, Christian L. Lengauer, Theodoros Ntaflos, Uwe Kolitsch, Ekkehart Tillmanns: Two new minerals, rondorfite, Ca 8 Mg [SiO 4] 4 Cl 2, and almarudite, K ( □, Na) 2 ( Mn, Fe, Mg) 2 (Be, Al) 3 [Si 12 O 30], and a study of iron-rich wadalite, Ca 12 [(Al 8 Si 4 Fe 2) O 32] Cl 6, from the Bellerberg ( Bellberg) volcano, Eifel, Germany . In: New Yearbook for Minaralogy Treatises . tape 179 , 2004, pp. 265–294 ( researchgate.net [PDF; 4.7 MB ; accessed on June 30, 2018]).
  9. ↑ R. Bailau, EV Galuskin, VM Gazeev, NN Pertzev: Classification and potential new minerals in the "mayenite" group. In: Acta Mineralogica Petrographica Abstract Series. 20th General Meeting of the International Mineralogical Association August 21-27, 2010. Budapest, Hungary . tape 6 , 2010, p. 493–493 ( rruff.info [PDF; 645 kB ; accessed on June 30, 2018]).
  10. ↑ a b c d e Evgeny V. Galuskin, Frank Gfeller, Irina O. Galuskina, Thomas Armbruster, Radu Bailau, Viktor V. Sharygin: Mayenite supergroup, part I: Recommended nomenclature . In: European Journal of Mineralogie . tape 27 , 2014, p. 99–111 ( amazonaws.com [PDF; 802 kB ; accessed on June 30, 2018]).
  11. ↑ Chi Ma, Alexander N. Krot: Adrianite, Ca12 (Al4Mg3Si7) O32Cl6, a new Cl-rich silicate mineral from the Allende meteorite: An alteration phase in a Ca-Al-rich inclusion. In: American Mineralogist . In Press, 2018 ( minsocam.org [PDF; 1.5 MB ; accessed on July 22, 2018]).