Chloromayenite

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Chloromayenite
Chlormayenite.jpg
Pale yellow chloromayenite crystal from Ettringer Bellerberg , Eifel, Rhineland-Palatinate, Germany
General and classification
other names

IMA 1963-016, Mayenite, IMA 2010-062, brearleyite

chemical formula Ca 12 Al 14 O 32 [□ 4 Cl 2 ]
Mineral class
(and possibly department) 		Silicates and Germanates
Similar minerals Fluorkyuygenit , Chlorkyuygenit , Fluormayenit , Grossular
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  = 12.0320 (natural); synthetic: 12.00950  Å
Formula units Z  = 2
Physical Properties
Mohs hardness Please complete!
Density (g / cm 3 ) calculated: 2.85
Cleavage Please complete!
colour colorless
Line color White
transparency transparent
shine Please complete!
radioactivity -
magnetism -
Crystal optics
Refractive index n  = 1.643
Birefringence none, isotropic

The mineral chloromayenite is a rarely occurring oxide from the mayenite upper group with the idealized chemical composition Ca 12 Al 14 O 32 Cl 2 . It crystallizes in the cubic crystal system with the structure of the cement compound Ca 12 Al 14 O 33 .

Chlormayenite only develops very small, colorless crystals or round grains less than 0.1 mm in size.

Chlormayenite is formed at low pressure and high temperatures when calcium-rich sediments are converted by a chlorine-rich fluid . At lower temperatures and in the presence of water, chlormayenite is converted into chlorkyuygenite .

Etymology and history

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 elucidation, they corrected the composition to 12CaO · 7Al 2 O 3 , C 12 A 7 in the cement chemical notation .

The first finds of a natural, cubic calcium aluminate were made in 1963 by L. Heller in a Sprurrite rock in the Nalhal Ayalon outcrop of the Hatrurim Formation in Israel. It is a common mineral found in many outcrops of the Hatrurim Pyromethamorphic Formation.

A year later it was described as a new mineral by Gerhard Hentschel together with brownmillerite in limestone inclusions from lavas from Ettringer Bellerberg with the composition Ca 12 Al 14 O 33 . He named the new mineral after the nearby town of Mayen Mayenite .

The chlorine analog of C 12 A 7 , the compound 11CaO · 7Al 2 O 3  · CaCl 2 or Ca 12 Al 14 O 32 Cl 2 , was synthesized in 2008 by Tomoyuki Iwata and co-workers at Nagoya Technical University in Nagoya , Japan , and the structure examined.

Two years later, Chi Ma et al . Described the first natural occurrence of this compound in the NWA 1934 meteorite , a CV3 chondrite from northwest Africa. Ca 12 Al 14 O 32 Cl 2 was initially recognized as a new mineral by the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the IMA under the name Brearleyite, after the mineralogist Adrian J. Brearley of the University of New Mexico .

In the course of the redefinition of the upper Mayenite group since 2010, Mayenites from various sites were re-examined, including the Mayenite from Ettringer Bellerberg. The composition given by Hentschel could not be confirmed. The mayenite from the type locality contains chlorine and its composition is similar to that of the brearleyite. Mayenite and Brearleyite were then discarded as mineral names and the new name chloromayenite was introduced for the mineral with the ideal composition Ca 12 Al 14 O 32 [□ 4 Cl 2 ]. The old name mayenite has survived in the materials science literature and is reserved as a mineral name for a natural occurrence of the compound Ca 12 Al 14 O 32 [□ 5 O] (C 12 A 7 ).

classification

In the current classification of the International Mineralogical Association (IMA), chlormayenite belongs to the mayenite group with less than 4 Cl and 2 Si per formula unit together with fluoromayenite , chlororkyuygenite and fluorokyuygenite in the mayenite upper group.

The outdated, but still in use, 8th edition of the mineral classification according to Strunz still lists chloromayenite under the disapproved name of mayenite. Here he is with brownmillerite and Srebrodolskit in the "brownmillerite mayenite group" with the system no. IV / A.07 in the department of "Oxides and Hydroxides".

The 9th edition of Strunz's mineral systematics, which has been valid since 2001 and is used by the IMA, also lists chloromayenite with the outdated name mayenite. Here it is the only mineral in the unnamed group with the system no. 4.CC.20 in the department of "Oxides (hydroxides, V [5,6] -vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)".

The systematics of minerals according to Dana , which is mainly used in the English-speaking area , also lists chloromayenite as mayenite. It is the only mineral here in the unnamed group 11/07/03 of the department of "Multiple Oxides".

Chemism

Chloromayenite with the idealized composition [X] Ca 12 [T] Al 3+ 14 O 32 [W] [□ 4 Cl 2 ] is the chlorine analog of fluoromayenite ( [X] Ca 12 [T] Al 3+ 14 O 32 [W] [□ 4 F 2 ]), where [X], [T] and [W] are the positions in the mayenite structure and □ (blank) stands for an unoccupied grid position.

The composition of chlormayenite from the type localities of mayenite and brearleyite is

  • Ettringer Bellerberg: [X] Ca 12 [T] (Al 13.513 Fe 3+ 0.456 Mg 0.012 Si 0.007 Ti 0.003 ) O 31.324 (OH) 2.028 [W] [□ 4.581 Cl 1.323 ]
  • Meteorite NWA 1934: [X] (Ca 11.91 Na 0.06 ) [T] (Al 13.89 Fe 3+ 0.16 Ti 0.01 ) O 31.89 [W] [□ 3.89 Cl 2 , 11 ]

The deviations from the ideal composition are essentially due to two rows of mixed crystals . On the one hand, Fe 3+ is incorporated in the [T] positions, corresponding to the exchange reaction

  • [T] Al = [T] Fe 3+ (hypothetical Fe analog of chloromayenite),

on the other hand, the mixture with the hypothetical (OH) analog [X] Ca 12 [T] Al 3+ 14 O 30 (OH) 6 [W] [□ 6 ] leads to the exchange of oxygen (O 2- ) and chlorine ( Cl - ) through 3 (OH) according to the reaction

  • [O2] O 2- + 3 [O2a] □ + [W] Cl - = [O2] □ + 3 [O2a] (OH) - + [W] □.

Furthermore, z. B. zoned chloromayenite-wadalite crystals from burned coal heaps and Si-Cl-rich chloromayenites from xenolites of the Chengem caldera a complete mixed crystal row with wadalite corresponding to the exchange reaction

  • [T] Al 3+ + [W] □ = [T] Si 4+ + [W] Cl -

Finds of Cl- and F-containing Mayenites in different outcrops of the Hatrurim Formation in Israel, Jordan and Palestine show a mixed crystal formation of chloromayenite and fluoromayenite:

  • [W] Cl - = [W] F -

Crystal structure

Chloromayenite 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  = 12.0320  Å . Template: room group / 220

The structure is that of the cement compound Ca 12 Al 14 O 33 . Aluminum (Al 3+ ) occupies the two tetrahedral T-positions surrounded by 4 oxygen ions. 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. In their center between the calcium ions, 1/3 of the cages contain a chlorine ion (Cl - ).

The substitution of an oxygen in the O2 position and a chlorine ion in the W position by three OH groups in the otherwise unoccupied O2a position leads to an increase in the coordination number of the neighboring aluminum in a T1 position from 4 to 6. In the chloromayenite of the type locality In this way, around 10% of the aluminum ions on T1 are octahedrally surrounded by 6 oxygen.

Education and Locations

Greenish jasmundite crystal aggregate with chloromayenite (yellow) from Ettringer Bellerberg , Eifel, Rhineland-Palatinate, Germany

Chlormayenite forms pyrometamorphically or contact metamorphically at low pressure and high temperatures when calcium-rich sediments are converted by a chlorine-rich fluid . In meteorites, chloromayenite is a conversion product of primary calcium aluminates ( crotite ) by a chlorine-rich fluid. With fluids rich in water, chloromayenite can be converted into chlorinated hydrogenite.

Skarne

The type locality of Chlormayenit is a kontaktmetamorpher skarn - Xenolith from the leucite - tephrite of Mayener field at Southern lava flow of Bellerberg volcano in Ettringen near Mayen in the Eifel , Rhineland-Palatinate ( Germany ). It occurs here together with ettringite , calcite , wollastonite , gehlenite , larnite , diopside , brownmillerite , grossular , pyrrhotite , spinel , afwillite , hydrocalumite and portlandite .

Similar occurrences are the xenoliths from the olivine - nephelinite from Emmelberg at Uedersdorf near Daun in the Eifel and the nepheline - basanite in Balastseinbruch in Kloch near Bad Radkersburg in Styria in Austria .

In several outcrops of the Hatrurim Formation in Israel , Palestine and Jordan , chlormayenite and fluoromayenite could be detected in pyrometamorphic calcareous silicate rocks.

Meteorites

In the NWA 1934 meteorite , a CV3 chondrite from northwest Africa, chloromayenite is found in a crotite -rich calcium-aluminum-rich inclusion (CAI) together with hercynite , perovskite and gehlenite. It is believed that chloromayenite was formed when crotite reacted with a Cl-rich gas

  • 12 CaAl 2 O 4 (crotite) + Cl 2 (gas) = ​​Ca 12 Al 14 O 32 Cl 2 (chloromayenite) + 5 Al 2 O 3 ( corundum ) + 0.5 O 2

The corundum reacted further with iron oxide from a fluid to form Herzynit:

  • Al 2 O 3 (corundum) + FeO (gas) = ​​FeAl 2 O 4 (hercynite)

Pyrometamorphic clinker from coal heaps

In a lime silicate brick tuber from the spent slag heap of Kalinin coal mine in the Donets Basin , Ukraine , Chlormayenit was with spurrite , Kumtyubeit , oldhamite , Jasmundit , Larnite, brownmillerite, wadalite and Cuspidin found.

Similar deposits can be found in coal tailings in Russia , Poland and the Czech Republic .

Web links

Commons : Chlormayenite  - collection of images, videos and audio files

Individual evidence

  1. ↑ Chlormayenit at mindat.org
  2. ↑ a b Evgeny V. Galuskin, Frank Gfeller, Thomas Armbruster, Irina O. Galuskina, Yevgeny Vapnik, Mateusz Dulski, Mikhail Murashko, Piotr Dzierzanowsky, Viktor V. Sharygin, Sergey V. Krivovichev and Richard Wirth: Mayenite supergroup, part III: Chlormayenite, Ca12Al14O32 [ 〈4 F2], and fluorkyuygenite, Ca12Al14O32 [(H2O) 4F2], two new minerals from pyrometamorphic rocks of the Hatrurim Complex, South Levant . In: European Journal of Mineralogie . tape 27 , 2015, p. 123-136 ( researchgate.net [PDF; 689 kB ; accessed on July 28, 2018]).
  3. ↑ a b c d e f g h i j k l m n o p q r EV GALUSKIN, J. KUSZ, T. ARMBRUSTER, R. BAILAU, IO GALUSKINA, B. TERNES AND M. MURASHKO: A reinvestigation of mayenite from the type locality, the Ettringer Bellerberg volcano near Mayen, Eifel district, Germany . In: Mineralogical Magazine . tape 76 , 2012, p. 707-716 ( rruff.info [PDF; 388 kB ; accessed on July 29, 2018]).
  4. ↑ a b Tomoyuki Iwata, Masahide Haniuda, Koichiro Fukuda: Crystal structure of Ca12Al14O32Cl2 and luminescence properties of Ca12Al14O32Cl2: Eu2 + . In: Journal of Solid State Chemistry . tape 181 , 2008, p. 51-55 , doi : 10.1016 / j.jssc.2007.11.002 .
  5. ↑ a b c d Michael Fleischer: New Mineral Names - Mayenite . In: The American Mineralogist . tape 50 , 1965, pp. 2096–2111 ( rruff.info [PDF; 1,3 MB ; accessed on July 29, 2018]).
  6. ↑ a b EV Galuskin, IO Galuskina, J. Kusz, F. Gfeller, T. Armbruster, R. Bailau, M. Dulski, VM Gazeev, NN Pertsev, AE Zadov, P. Dzierzanowski: supergroup Mayenite, part II: Chlorkyuygenite from northern Caucasus Kabardino-Balkaria, Russia, a new microporous mayenite supergroup mineral with `` zeolitic '' H2O. In: European Journal of Mineralogie . tape 27 , 2015, p. 123-136 , doi : 10.1127 / ejm / 2015 / 0027-2419 .
  7. ↑ Ernest Stanley Shepherd and 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 .
  8. ↑ 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]).
  9. ^ A b S. Gross: The mineralogy of the Hatrurim formation, Israel. In: Geol. Surv. Isr. Bull. Band 70 , 1977, pp. 1–80 ( rruff.info [PDF; 5.7 MB ; accessed on July 29, 2018]).
  10. ^ A b Chi Ma, Stuart A. Sweeney Smith, Harold C. Connolly Jr., John R. Beckett, George R. Rossman, Devin L. Schrader: Discovery of Cl-bearing mayenite, Ca12Al14O32Cl2, a new mineral in a CV3 Meteorite . In: 73rd Annual Meteoritical Society Meeting . 2010, p. 5134-5134 ( rruff.info [PDF; 82 kB ; accessed on July 29, 2018]).
  11. ↑ a b c d Chi Ma, Harold C. Connolly Jr., John R. Beckett, Oliver Tschauner, George R. Rossman, Anthony R. Kampf, Thomas J. Zega, Stuart A. Sweeney Smith and Devin L. Schrader: Brearleyite , Ca12Al14O32Cl2, a new alteration mineral from the NWA 1934 meteorite. In: The American Mineralogist . tape 96 , 2011, p. 1199–1206 ( rruff.info [PDF; 539 kB ; accessed on August 7, 2018]).
  12. ↑ a b c d e f g Evgeny V. Galuskin, Frank Gfeller, Irina O. Galuskina, Thomas Armbruster, Radu Bailau and 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]).
  13. ↑ a b Victor Victorovich Sharygin: Mayenite-supergroup minerals from burned dump of the Chelyabinsk Coal Basin . In: Russian Geology and Geophysics . tape 56 , 2015, p. 1603–1621 ( researchgate.net [PDF; 7.1 MB ; accessed on June 30, 2018]).
  14. ↑ a b List of sites for chloromayenite in the Mineralienatlas and Mindat
  15. ↑ Victor Victorovich Sharygin: Mineralogy of Ca-rich Metacarbonate Rocks from Burned Dumps of the Donetsk Coal Basin . 2010, p. 162–170 ( researchgate.net [PDF; 563 kB ; accessed on June 30, 2018]).
  16. ↑ Pavla HRŠELOVÁ, Jan CEMPÍREK, Stanislav HOUZAR, Jiří SEJKORA: S, F, Cl-RICH MINERAL ASSEMBLAGES FROM BURNED SPOIL HEAPS IN THE ROSICE-OSLAVANY COALFIELD, CZECH REPUBLIC . In: The Canadian Mineralogist . tape 51 , 2013, p. 171–188 ( researchgate.net [PDF; 5.7 MB ; accessed on August 11, 2018]).