Arctite

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Arctite
Arctite.jpg
transparent to white, granular arctite crystals with pink villiaumite from the Vuonnemiok river valley, Kola peninsula , Russia
General and classification
other names
  • IMA 1980-049
  • Arctite (after Werner) is scapolite
chemical formula
  • (Na 5 Ca) Ca 6 Ba (PO 4 ) 6 F 3
  • Na 5 BaCa 7 [F 3 | (PO 4 ) 6 ]
  • Na 5 Ca 7 Ba [F | (PO 4 ) 2 ] 3
  • Na 2 Ca 4 (PO 4 ) 3 F.
Mineral class
(and possibly department) 		Phosphates, arsenates and vanadates
System no. to Strunz
and to Dana 		8.BN.10
41.05.18.01
Crystallographic Data
Crystal system trigonal
Crystal class ; symbol ditrigonal-scalenohedral; 3  2 / m
Space group R 3 m (No. 166)Template: room group / 166
Lattice parameters a  = 7.09  Å ; c  = 41.32 Å
Formula units Z  = 3
Physical Properties
Mohs hardness 5
Density (g / cm 3 ) measured: 3.13; calculated: 3.19
Cleavage completely after {0001}
Break ; Tenacity brittle
colour colorless to white
Line color White
transparency transparent to translucent
shine Glass gloss, pearlescent
Crystal optics
Refractive indices n ω  = 1.578
n ε  = 1.577
Birefringence δ = 0.001
Optical character uniaxial negative

Arctite is a very rare mineral from the mineral class of "phosphates, arsenates and vanadates" with the chemical composition Na 5 BaCa 7 [F 3 | (PO 4 ) 6 ] or in the internationally recognized spelling (Na 5 Ca) Ca 6 Ba (PO 4 ) 6 F 3 . Arctit is thus a sodium - barium - calcium - phosphate with additional fluorine - ions .

Arctit crystallizes in the trigonal crystal system and develops colorless to white crystals up to three centimeters in size with a glass-like sheen on the surfaces.

Etymology and history

Arctite was first discovered in 1980 in a drill core from the Vuonnemiok river valley in the eastern part of the Chibinen and about 20 km west of Lake Umbosero (Lake Umba) on the Russian Kola Peninsula . The mineral was first described in 1981 by AP Khomyakov, AV Bykova and TA Kurova, who named it after the Arctic zone in which its type locality is located.

The chemical formula Na 2 Ca 4 (PO 4 ) 3 F given in the first description was corrected in 1984 by Elena V. Sokolova, NA Yamnova, YK Egorov-Tismenko and AP Khomyakov to Na 5 BaCa 7 (PO 4 ) 6 F 3 after Their structural analyzes showed that they corresponded better to the results of the analysis.

The type material of the mineral is obtained from the Mining Institute of Saint Petersburg under catalog no. 120/1 , in the Geological Museum of the Russian Academy of Sciences in Apatity under catalog no. 5708/2 and in the Mineralogical Fersman Museum in Moscow under catalog no. 82132 and in the Natural History Museum in London (England) under catalog no. 1994.2 kept.

classification

Since the Arctite was only discovered in 1980 and recognized as an independent mineral, it is not listed in the 8th edition of the mineral classification according to Strunz, which has been outdated since 1977 . Only in the Lapis mineral directory , which was revised and updated in 2018 by Stefan Weiß, which is still based on this classic system from Karl Hugo Strunz out of consideration for private collectors and institutional collections , the mineral received the system and mineral number. VII / B.21-20 . In the "lapis system" this corresponds to the class of "phosphates, arsenates and vanadates" and there the department "anhydrous phosphates, with foreign anions F, Cl, O, OH", where Arctite together with Abuit , Moraskoite and Nefedovite are independent , but forms an unnamed group.

The 9th edition of Strunz's mineral systematics, valid since 2001 and updated by the International Mineralogical Association (IMA) until 2009, also assigns Arctite to the department of “phosphates etc. with additional anions; without H 2 O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of the additional anions to the phosphate, arsenate or vanadate complex, so that the mineral is classified in the sub-section “With only large cations; (OH etc.): RO 4  = 0.33: 1 “can be found where it is the only member of the unnamed group 8.BN.10 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Arctite to the class of "phosphates, arsenates and vanadates" and there in the department of "anhydrous phosphates etc., with hydroxyl or halogen". Here he is the only member of the unnamed group May 41, 2018 within the subsection “Anhydrous phosphates etc., with hydroxyl or halogen with (AB) 2 (XO 4 ) Z q ”.

Crystal structure

Arctite crystallizes trigonal in the space group R 3 m (space group no. 166) with the lattice parameters a  = 7.09  Å and c  = 41.32 Å as well as three formula units per unit cell . Template: room group / 166

The crystal structure of Arctit consists of three differently structured layers parallel to the surfaces (0001). In the first layer 12x are coordinated barium atoms (Ba [12] ) icosahedral about PO 4 - tetrahedra linked. The second layer is formed by triplets of edge-sharing Ca [7] polyhedra with PO 4 tetrahedra and fluorine atoms, and in the third layer Ca [7] polyhedra are linked to one another via shared areas. The layers are each connected via PO 4 tetrahedra.

properties

Arcit is insoluble in water, but it can be dissolved in dilute (1:20 or 5%) hydrochloric acid (HCl).

Education and Locations

Arctite forms in the late phase of pneumatolytic rock transformation in pegmatitic veins that penetrate differentiated alkali massifs. As Begleitminerale occur among other Aegirin , Kostylevit , Lomonosovit , Natisit , natrosilite , Paraumbit , Rasvumit , Thenardite , Umbit , Villiaumit , Vuonnemit , Wadeit and Zirsinalith on.

Arctite is one of the very rare mineral formations that is known only in a few samples from 4 documented sites so far, all of which are so far in the Chibinen on the Russian Kola Peninsula (as of 2019). In addition to its type locality , the Vuonnemiok river valley, the mineral was also found on the Koaschwa in mineral samples from the Koaschwa open-cast mine (also Vostochnyi Mine ) and at the IGC Stop 2-3 in samples collected during an excursion. In addition, Arctite could still be discovered in mineral samples that were collected at Rischorr .

See also

literature

  • AP Khomyakov, AV Bykova, TA Kurova: АРКТИТ N а 2 Са 4 ( РО 4 ) 3 F - новый МИНЕРАЛ . In: Zapiski Vsesoyuznogo Mineralogicheskogo Obshchestva . tape 110 , no. 4 , 1981, p. 506–508 (Russian, available online at rruff.info [PDF; 185 kB ; accessed on May 1, 2019]).
  • Michael Fleischer , Louis J. Cabri, GY Chao, JA Mandarino, Adolf Pabst : New mineral names . In: American Mineralogist . tape 67 , 1982, pp. 621–624 (English, available online at rruff.info [PDF; 817 kB ; accessed on May 1, 2019]).
  • Elena V. Sokolova, NA Yamnova, YK Egorov-Tismenko, AP Khomyakov: Crystal structure of arctite, a new sodium calcium barium phosphate (Na 5 Ca) Ca 6 Ba [PO 4 ] 6 F 3 . In: Soviet Physics - Doklady . tape 29 , 1984, pp. 5–8 ( available online at researchgate.net [accessed May 1, 2019]).
  • EV Sokolova, NA Yamnova, YK Egorov-Tismenko, AP Khomyakov: КРИСТАЛЛИЧЕСКАЯ СТРУРА НОВОГО ФОСФАТА Na, Ca и Ba (Na 5 Ca) Ca 6 Ba [PO 4 ] 6 F 3 . In: Doklady Akademii Nauk SSSR . tape 274 , 1984, pp. 78–83 (Russian, available online at rruff.info [PDF; 419 kB ; accessed on May 1, 2019]).
  • Andrei Arzamastsev, Victor Yakovenchuk, Yakov Pakhomovsky, Gregory Ivanyuk: The Khibina and Lovozero alkaline massifs: Geology and unique mineralization . In: Guidebook for 33rd International Geological Congress Excursion . tape 47 , 2008, p. 27 (English, available online at iugs.org [PDF; 4.1 MB ; accessed on May 2, 2019]).

Web links

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

Individual evidence

  1. ↑ a b c Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: March 2019. (PDF 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, March 2019, accessed May 1, 2019 .
  2. ↑ a b c d e f g 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.  468 (English).
  3. ↑ a b c Stefan Weiss: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
  4. ↑ a b Michael Fleischer , Louis J. Cabri, GY Chao, JA Mandarino, Adolf Pabst : New mineral names . In: American Mineralogist . tape  67 , 1982, pp. 621–624 (English, available online at rruff.info [PDF; 817 kB ; accessed on May 1, 2019]).
  5. ↑ a b c d Arctite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 63  kB ; accessed on May 1, 2019]).
  6. ↑ a b c Arctite. In: mindat.org. Hudson Institute of Mineralogy, accessed May 1, 2019 .
  7. ^ Igor V. Pekov: Minerals first discovered on the territory of the former Soviet Union . 1st edition. Ocean Pictures, Moscow 1998, ISBN 5-900395-16-2 , pp. 28 .
  8. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed May 1, 2019 .
  9. ↑ Richard V. Gaines, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason , Abraham Rosenzweig: Dana's New Mineralogy . 8th edition. John Wiley & Sons, New York et al. 1997, ISBN 0-471-19310-0 , pp. 843 .
  10. ↑ Find location list for Arctite in the Mineralienatlas and Mindat