Adrianite

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Adrianite
General and classification
other names

IMA 2014-028

chemical formula
  • Ca 12 (Al 4 Mg 3 Si 7 ) O 32 Cl 6
Mineral class
(and possibly department) 		Silicates and Germanates
System no. according to Strunz 9.AD.25
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: 11.981  Å
Formula units Z  = 2
Physical Properties
Mohs hardness not determined
Density (g / cm 3 ) calculated: 3.03
Cleavage not determined
Break ; Tenacity not determined
colour not determined
Line color not determined
transparency not determined
shine not determined
Crystal optics
Refractive index n  = not determined
Birefringence δ = not determined

The mineral adrianite is an extremely rare island silicate from the mayenite upper group with the simplified chemical composition Ca 12 (Al 4 Mg 3 Si 7 ) O 32 Cl 6 (type locality) or Ca 12 (Mg 10 Si 4 ) O 32 Cl 6 (pure end link). It crystallizes in the cubic crystal system with the structure of chloromayenite .

Adrianite only develops very small crystals a few micrometers in size. Because of the small grain size , many properties could not be determined.

Adrianite is formed below 600 ° C during the conversion of melilite, perovskite and diopside into calcium-aluminum-rich inclusions (CAI) of chondritic meteorites by fluids rich in chlorine .

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 determination, they corrected the composition to 12CaO * 7Al 2 O 3 .

Wadalite, 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 . 17 years later, in 2010, wadalite could be detected for the first time in a meteorite.

In the same year Mihajlovic and co-workers described an iron-rich wadalite from a carbonate xenolite from the leucite - tephrite , which is and was able to be mined in the quarry of the company "A. Caspar" on the Bellerberg volcano near Mayen in the Vulkaneifel in Rhineland-Palatinate , Germany show that its composition is also varied by mixing it with a hypothetical Mg-Si analog of wadalite.

In 2014, the mineral adrianite with the idealized composition of this Mg-Si analogue of wadalite was finally detected in the Allende meteorite and recognized by the CNMNC of the IMA. It was named after the mineralogist and cosmochemist Adrian J. Brearley of the University of New Mexico in recognition of his numerous contributions to the mineralogy of meteorites.

The publication of the description of Adrianit dragged on until 2018. Adrianite was therefore mentioned in the redefinition of the wadalite group in the mayenite upper group by E. V. Galuskina and co-workers, but no longer considered.

classification

In the current classification of the International Mineralogical Association (IMA), adrianite belongs together with wadalite and eltyubyuit in the mayenite upper group to the wadalite group with more than 4 Cl and 2 Si per formula unit.

The 8th edition of the mineral classification according to Strunz , which has been obsolete since 1977 , does not list Adrianite. As a magnesium-silicon analog of Wadalit, it would be part of the “garnet group” with system no. VIII / A.08 in the department of " island silicates (nesosilicates)".

The 9th edition of Strunz's mineral systematics, which has been valid since 2001 and was updated by the International Mineralogical Association (IMA) until 2009 , does not yet know the Adrianite 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)".

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

Chemism

The pure adrianite end member has the composition [X] Ca 12 [T] (Mg 2+ 10 Si 4+ 4 ) O 32 [W] Cl 6 and is the magnesium - silicon analog 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] Mg 2+ + [T] Si 4+ = 2 [T] Al 3+ (wadalite).

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

The composition from the type locality is

  • [X] (Ca 11.69 Na 0.21 ) [T] (Al 3.85 Mg 2.88 Si 7.23 ) O 32 [W] [Cl 5.80 □ 0.20 ]

In addition to the mixed crystal formation with wadalite, which is responsible for the incorporation of aluminum, only one other substitution contributes to a lowering of the Cl content, which has not been observed in any other mineral of the mayenite upper group so far (2018) :

  • [X] Ca 2+ + [W] Cl - = [X] Na + + [W] □

Crystal structure

Adrianite 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  = 11.981  Å . Template: room group / 220

The structure is that of chlormayenite . Magnesium (Mg 2+ ) and silicon (Si 4+ ) occupy 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. The cages contain a chlorine ion (Cl - ) in their center between the calcium ions . As with all minerals of the wadalite group, the [W] position is ideally completely occupied.

Education and Locations

Adrianite is so far (2018) only known from its type locality , the Allende meteorite, which fell on February 8, 1969 not far from the post office of the town of Pueblito de Allende ( state of Chihuahua , Mexico ). Adrianite is not a primary component of this chondrite , but was formed during the transformation of melilite , perovskite and diopside into calcium-aluminum-rich inclusions (CAI) by fluids rich in chlorine . There will be a formation 3–4 * 10 9 years after the formation of CAI at temperatures below 600 ° C z. B. about the reaction

accepted.

Adrianite occurs only in the converted areas of the calcium-aluminum-rich inclusions. There you can find him in direct contact with Melilith, Grossular and Monticellit. Other accompanying minerals are the primary minerals anorthite , wollastonite , Al, Ti-diopside, perovskite, spinel , forsterite and celsian as well as the secondary minerals hutcheonite, kushiroite and wadalite .

literature

  • Chi Ma, Alexander N. Krot: Adrianite, Ca 12 (Al 4 Mg 3 Si 7 ) O 32 Cl 6 , a new Cl-rich silicate mineral from the Allende meteorite: An alteration phase in a Ca-Al-rich inclusion . In: American Mineralogist . tape 103 , no. 8 , 2018, p. 1329–1334 , doi : 10.2138 / am-2018-6505 , PMC 6448150 (free full text) - (English).
  • PA Williams, F. Hatert, Marco Pasero, SJ Mills: IMA Commission on new minerals, nomenclature and classification (CNMNC) Newsletter 21 . New minerals and nomenclature modifications approved in 2014. In: Mineralogical Magazine . tape 78 , 2014, p. 797–804 (English, rruff.info [PDF; 99 kB ; accessed on January 11, 2020]).

Web links

Individual evidence

  1. ↑ a b Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: November 2019. (PDF 1720 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, November 2019, accessed January 11, 2020 .
  2. ↑ a b c d e f g h i Chi Ma, Alexander N. Krot: Discovery of a new Cl-rich silicate mineral, Ca 12 (Al 2 Mg 3 Si 7 ) O 32 Cl 6 : an alteration phase in Allende . In: Annual Meteoritical Society Meeting . tape 77 , 2014 ( hou.usra.edu [PDF; 256 kB ; accessed on January 11, 2020]).
  3. ↑ a b c d e f g h i j k l m n o p q r Chi Ma, Alexander N. Krot: Adrianite, Ca 12 (Al 4 Mg 3 Si 7 ) O 32 Cl 6 , a new Cl-rich silicate mineral from the Allende meteorite: An alteration phase in a Ca-Al-rich inclusion . In: American Mineralogist . tape 103 , no. 8 , 2018, p. 1329–1334 , doi : 10.2138 / am-2018-6505 , PMC 6448150 (free full text) - (English).
  4. ↑ Adrianite. In: mindat.org. Hudson Institute of Mineralogy, accessed January 11, 2020 .
  5. ^ 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 .
  6. ↑ 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 January 11, 2020]).
  7. ↑ K. Tsukimura, Y. Kanazawa, M. Aoki, M. Bunno: Structure of wadalite Ca 6 Al 5 Si 2 O 16 Cl 3 . In: Acta Crystallographica, Section C . C49, 1993, pp. 205-207 , doi : 10.1107 / S0108270192005481 .
  8. ↑ Hope A. Ishii, Alexander N. Krot, John P. Bradley, Klaus Keil, Kazuhide Nagashima, Nick Teslich, Benjamin Jacobsen, Qing-Zhu Yin: Discovery, Mineral Paragenesis and Origin of Wadalite in Meteorites . In: American Mineralogist . tape 95 , no. 4 , 2010, p. 440–448 , doi : 10.2138 / am.2010.3296 ( starplan.dk [PDF; 1,3 MB ; accessed on January 11, 2020]).
  9. ↑ a b 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 Minarogy, Treatises . tape 179 , 2004, pp. 265-294 , doi : 10.1127 / 0077-7757 / 2004 / 0179-0265 ( researchgate.net [PDF; 4.8 MB ; accessed on January 11, 2020]).
  10. ↑ a b 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 , doi : 10.1127 / ejm / 2015 / 0027-2418 ( researchgate.net [PDF; 860 kB ; accessed on January 11, 2020]).
  11. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1816 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed January 11, 2020 .