Fluorocyuygenite

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Fluorocyuygenite
General and classification
other names

IMA 2013-043

chemical formula Ca 12 Al 14 O 32 [(H 2 O) 4 F 2 ]
Mineral class
(and possibly department) 		Silicates and Germanates
Similar minerals Fluoromayenite, chloromayenite, chlorinated oxygenite
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  = 11.966 (natural)  Å
Formula units Z  = 2
Physical Properties
Mohs hardness 5 - 5.5
Density (g / cm 3 ) calculated: 2.873
Cleavage no
colour colorless, rarely pale green or yellow
Line color White
transparency transparent
shine Glass gloss
radioactivity -
magnetism -
Crystal optics
Refractive index n  = 1.610
Birefringence none, isotropic

The mineral fluorkyuygenite is a rarely occurring oxide from the mayenite upper group with the idealized chemical composition Ca 12 Al 14 O 32 [(H 2 O) 4 F 2 ]. It crystallizes in the cubic crystal system with the structure of chloromayenite .

Fluorkyuygenit develops only very small, colorless crystals of less than 0.1 mm in size. The crystals show well-developed surfaces of the triakis tetrahedron {211}.

Fluorkyuygenit is formed at low pressure and high temperatures during the conversion of calcium-rich sediments by a fluorine- and water-rich fluid .

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 structural analysis 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 Sprurrit 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 Mayenit .

The fluorine analog of mayenite, the compound 11CaO * 7Al 2 O 3  * CaF 2 , was synthesized in 1973 by PP Williams of the DSIR in Petone , New Zealand , and the structure was examined.

In the course of the redefinition of the Mayenite upper group since 2010, Mayenites from various sites were re-examined. All naturally occurring mayenites contain fluorine or chlorine , and the composition given by Hentschel could not be confirmed in any case. Mayenite was then discarded as a mineral name, new names were introduced and new minerals of the mayenite group were discovered, including fluorkyuygenite:

  • Chloromayenite for mayenite with the composition Ca 12 Al 14 O 32 [□ 4 Cl 2 ], z. B. from Ettringer Bellerberg
  • Chlorkyuygenit for hydrated chloromayenite (Ca 12 Al 14 O 32 [(H 2 O) 4 Cl 2 ])
  • Fluoromayenite for mayenite with the composition Ca 12 Al 14 O 32 [□ 4 F 2 ], z. B. from Jebel Harmun of the Hatrurim formation in Palestine
  • Fluorocyuygenite for hydrated fluoromayenite (Ca 12 Al 14 O 32 [(H 2 O) 4 F 2 ])

classification

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

The outdated, but still in use, 8th edition of the mineral classification according to Strunz does not list the fluorocyuygenite. As a fluorine analog of chlorinated cyuygenite, it would be part of the “Brownmillerite Mayenite Group” with system no. IV / A.07 in the department of “Oxides and Hydroxides”.

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 fluorocyuygenite either. Here he would with Mayenit 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 world , does not yet list fluorinated cyuygenite. Together with Mayenit he would be grouped in the unnamed group 11/07/03 of the department of "Multiple Oxides".

Chemism

Fluorocyuygenite with the idealized composition [X] Ca 12 [T] Al 3+ 14 O 32 [W] [(H 2 O) 4 F 2 ] is the fluorine analog of chlorocyuygenite ( [X] Ca 12 [T] Al 3 + 14 O 32 [W] [(H 2 O) 4 Cl 2 ]) and the H 2 O analogue 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 from the type locality is

  • [X] Ca 12.034 [T] (Al 13.344 Fe 3+ 0.398 Si 0.224 ) O 32 [W] [(H 2 O) 3.810 F 1.894 (OH) 0.296 □ 0.110 ]

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 analogue of fluorocyuygenite),

on the other hand, the mixture with the hypothetical (OH) analog [X] Ca 12 [T] Al 3+ 14 O 32 [W] [(H 2 O) 4 (OH) 2 ] leads to the incorporation of OH groups on the [W] position corresponding to the exchange reaction

  • [W] F - = [W] (OH) - .

The low Si contents together with the slightly increased contents of monovalent ions in the [W] position speak in favor of mixed crystal formation with a hypothetical fluorine or OH analog of wadalite.

  • [T] Al 3+ + [W] □ = [T] Si 4+ + [W] (OH, F) -

Crystal structure

Fluorkyuygenit 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  = 11.966  Å . Template: room group / 220

The structure is that of chlormayenite . Aluminum (Al 3+ ) occupies the two tetrahedral Z-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 fluorine ion (F - ), the other 4 [W] positions contain H 2 O.

Education and Locations

Fluorkyuygenit forms pyrometamorph at low pressure and high temperatures in the conversion of calcium-rich sediments by a fluorine rich, wässiges fluid or the hydration of Fluormayenit by a water-rich fluid.

So far (2018), fluoropyuygenite has only been detected in its type locality , the Hatrurim Basin southeast of the city of Arad in the Negev desert , Israel . He appears here in contact with Larnite , spinel , oldhamite and Shulamitit on. More Begleitminerale are ye'elimite , fluorapatite , Magnesioferrit , periclase , brownmillerite and minerals retrograde formed Portlandit , hematite , hillebrandite , Afwillit , Foshagite , katoite and hydrocalumites .

Web links

Individual evidence

  1. ↑ - Fluorocyuygenite
  2. ↑ a b c d e f g h i j k l m n o p q r s t u v w x y z 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: Fluormayenite, 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. ↑ 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 .
  4. ↑ 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]).
  5. ^ 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]).
  6. ↑ 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]).
  7. ^ PP Williams: Refinement of the structure of 11CaO.7Al2O3.CaF2 . In: Acta Crystallographica Section B . B29, 1973, p. 1550–1551 , doi : 10.1107 / S0567740873004942 .
  8. ↑ a b c d 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]).
  9. ↑ EV GALUSKIN, J. KUSZ, T. Armbruster, R. BAILAU, IO GALUSKINA, B. TERNES AND M. Murashko: A reinvestigation of mayenite from the type locality, district Ettringer the Bellerberg volcano near Mayen, Eifel, Germany . In: Mineralogical Magazine . tape 76 , 2012, p. 707-716 ( rruff.info [PDF; 388 kB ; accessed on July 29, 2018]).
  10. ↑ 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 ( researchgate.net ).