Zunyit

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Zunyit
Zunyite-199876.jpg
Zunyite crystals in the host rock of Silver City , East Tintic Mountains, Juab County , Utah, USA
General and classification
chemical formula
  • Al 12 [(OH) 14 | F 4 | Cl | AlO 4 | Si 5 O 16 ]
  • Al 13 Si 5 O 20 (OH, F) 18 Cl
Mineral class
(and possibly department) 		Silicates and Germanates
System no. to Strunz
and to Dana 		9.BJ.55 ( 8th edition : VIII / C.36)
57.03.01.01
Crystallographic Data
Crystal system cubic
Crystal class ; symbol cubic-hexakistrahedral; 4  3  m
Space group F 4 3 m (No. 216)Template: room group / 216
Lattice parameters a  = 13.88  Å
Formula units Z  = 4
Twinning after {111} contact and penetration twins
Physical Properties
Mohs hardness 7th
Density (g / cm 3 ) measured: 2.874 (5); calculated: 2.87 to 2.90
Cleavage good after {111}
Break ; Tenacity brittle
colour gray-white, flesh-red, colorless in thin layers
Line color White
transparency transparent to opaque
shine Glass gloss
Crystal optics
Refractive index n  = 1.592 to 1.600
Birefringence none, as isotropic
Other properties
Special features occasional red fluorescence

Zunyite is a rarely occurring minerals from the mineral class of "silicates and germanates" with the chemical composition Al 12 [(OH) 14 | F 4 | Cl | AlO 4 | Si 5 O 16 ], and chemical point of view so that an aluminum - silicate with additional Chlorine , fluorine and hydroxide ions . Structurally, Zunyit belongs to the group silicates .

Zunyit crystallizes in the cubic crystal system and usually develops well-formed tetrahedral or pseudo- octahedral crystals . In its pure form, Zunyite is colorless and transparent with a glass-like sheen on the crystal surfaces. However, due to multiple light refraction due to lattice construction defects or polycrystalline formation, it can also appear white, with the transparency decreasing accordingly. In addition, Zunyit can take on a gray-white to flesh-red color through foreign admixtures.

With a Mohs hardness of 7, Zunyite is one of the hard minerals that, like the reference mineral quartz , is able to scratch window glass.

Etymology and history

Zunyit was first discovered in the "Zuni Mine" (Zuñi Mine) on Anvil Mountain near Silverton in the US state of Colorado and described in 1883 by William Francis Hillebrand (1853-1925), who named the mineral after its type locality .

The type material of the mineral is in the collection of the National Museum of Natural History in Washington, DC (USA) under the catalog no. 049082 kept.

classification

Already in the outdated 8th edition of the mineral classification according to Strunz , the Zunyite belonged to the mineral class of "silicates and germanates" and there to the department of " group silicates (sorosilicates)" with the subdivision "With linear Si 3 O 10 groups", where it was classified as the only member of the unnamed group VIII / B.20 formed.

In the Lapis mineral directory according to Stefan Weiß, which, out of consideration for private collectors and institutional collections, is still based on this old form of Karl Hugo Strunz's system , the mineral was given the system and mineral number. VIII / C.36-10 . In the “Lapis system” this also corresponds to the “Group silicates” department, where Zunyit is the only member of the unnamed group VIII / C.36 (as of 2018).

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and was updated by the International Mineralogical Association (IMA) until 2009, also classifies Zunyit in the group of “group silicates”. However, this is further subdivided according to the structure of the silicate groups, the possible presence of further anions and the coordination of the cations involved , so that the mineral is classified in the sub-section “Group silicates with Si 3 O 10 , Si 4 O 11 , etc. ” according to its composition and structure . Anions; Cations in octahedral [6] and / or greater coordination ”can be found, where it is the only member of the unnamed group 9.BJ.55 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking area , also assigns the Zunyit to the class of "silicates and Germanates", but there in the more finely subdivided division of "group silicates: insular (Si 3 O 10 ) and larger non-cyclic groups with Si 3 O 10 groups ”. Here he is to be found as the only member of the unnamed group 57.03.01 within the subdivision of " Group silicates: Insular (Si 3 O 10 ) and larger non-cyclic groups with Si 5 O 16 groups ".

Crystal structure

Openly branched triple silicate group of Zunyite
Al-13 Keggin complex of Zunyit: gray: outer Al octahedron; green: central Al tetrahedron

Zunyit crystallizes cubically in the space group F 4 3 m (space group no. 216) with the lattice parameter a  = 13.88  Å and 4 formula units per unit cell . Template: room group / 216

Silicate group According to Liebau's classification , Zunyit is an openly branched 3-single-group silicate. The silicate group consists of a total of five silicate tetrahedra with the partial formula [Si 5 O 16 ] 12- , which are connected to one another at the corners via shared oxygen atoms. Three of the tetrahedra form a chain, from whose central tetrahedron two individual silicate tetrahedra branch off openly. The almost linear Si-O-Si bond with an angle of around 170 ° is unusual for silicates.

In the central SiO 4 tetrahedron, Si 4+ can be partially replaced by Al 3+ . In synthetic Zunyit, the replacement of SiO 4 by (OH) 4 could also be detected, as it is e.g. B. also occurs in hydro grenades.

Zunyit is the only silicate with this silicate pentamer. Only the [AlSi 4 (O, OH) 16 ] complex anion of Harkenite and the [MgSi 4 O 16 ] complex anion of Rondorfit are comparable .

Aluminum assembly Aluminum is surrounded both tetrahedrally by 4 oxygen and octahedral by 6 oxygen and fluorine and forms Al 13 O 16 (OH) 24 assemblies with the structure of Keggin complex ions .

Three AlO 4 (OH, F) 2 octahedra are linked by common edges. Four of these groups of three are connected via corners (shared oxygen) in such a way that they enclose a cavity with AlO 4 tetrahedra in the center . The corners of this tetrahedron lie on the central oxygen of the Al octahedron groups of three. These Al 13 O 16 (OH) 24 -Keggin complexes are connected to one another via common octahedron corners and the [Si 5 O 16 ] anions.

Such Keggin complex ions play an important role in the solubility of aluminum and other metals. Al-13 complexes occur except in Zunyit mainly in aluminum salts (sulfates, selenates) and their solutions.

properties

Some Zunyites show red fluorescence under UV light .

Education and Locations

Zunyit forms in high-grade aluminous schists and hydrothermally formed volcanic rocks . Accompanying minerals include alunite , diaspore , hematite , kaolinite , pyrite , pyrophyllite , quartz and rutile .

As a rare mineral formation, Zunyite could only be detected at a few sites, with around 100 sites being documented so far (as of 2020). In addition to its type locality "Zuni Mine", the mineral was found in the USA in several places in the Dome Rock Mountains , near San Manuel ( Pinal County ) and Alum Gulch ( Santa Cruz County ) in Arizona; on Mount Robinson ( Custer County ) on Horse Creek ( Dolores County ), in the Red Mountains ( Ouray County ) in Saguache County and at other locations in San Juan County , Colorado; at Butte in Montana; Buckskin ( Douglas County ), Scraper Springs ( Elko County ) and Robinson ( White Pine County ), Nevada; at Clubb Mountain and Hillsborough in North Carolina and in the Tintic Mountains in Utah .

Other sites are in Bejaia in Algeria; King George Island in Antarctica; Catamarca , La Rioja and Salta in Argentina; on Tasmania in Australia; in Azerbaijan ; at Cerro Tazna in the Bolivian Cordillera de Chichas ; Brumado in the Brazilian state of Bahia ; near Panagyurishte and Chelopech ( Sofia Oblast ) in Bulgaria; in several places in the Región de Atacama in Chile; in Zijinshan and Qinglong (Qinhuangdao) in China; on Honshū in Japan; on Vancouver Island in Canada; at Ojuu Tolgoi in Mongolia; in the Moroccan province of Ouarzazate (Souss-Massa-Draâ); near Otuzco in the Peruvian province of La Libertad ; in Mankayan in the Philippines; in the Apuseni Mountains in Romania; at Bor in Serbia; in the Slovak regions of Banská Bystrica and Košice ; in the Spanish province of Almería ; near Doornfontein on the North Cape in South Africa; in Fejér County, Hungary and near Embleton ( Cumbria ) in the United Kingdom.

See also

literature

  • WF Hillebrand: New mineral species from Colorado. Zunyite . In: Department of the Interior. Bulletin of the United States Geological Survey . tape 20 , 1885, p. 100–103 (English, pubs.usgs.gov [PDF; 8.1 MB ; accessed on April 24, 2020]).
  • WF Hillebrand: On Zunyite and guitermanite, two new minerals from Colorado . In: Proceedings of the Colorado Scientific Society . tape 1 , 1885, p. 124–131 (English, rruff.info [PDF; 550 kB ; accessed on April 24, 2020]).

Web links

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

Individual evidence

  1. ↑ a b c d e 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.  593 .
  2. ↑ Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: March 2020. (PDF; 2.44 MB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, March 2020, accessed April 24, 2020 .
  3. ↑ David Barthelmy: Zunyite Mineral Data. In: webmineral.com. Retrieved April 24, 2020 (English).
  4. ↑ a b c d e f Zunyite . 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; 70  kB ; accessed on April 24, 2020]).
  5. ^ LJ Spencer : Mineralogical chemistry . In: Annual reports on the progress of chemistry . tape  24 , 1927, pp. 292–313 , doi : 10.1039 / AR9272400292 (English, obituary for Paul Heinrich Ritter von Groth with appreciation for William Francis Hillebrand's analytical work).
  6. ↑ Catalog of Type Mineral Specimens - Z. (PDF 30 kB) In: docs.wixstatic.com. Commission on Museums (IMA), December 12, 2018, accessed April 24, 2020 .
  7. ↑ 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 .
  8. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF; 1.82 MB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed April 24, 2020 .
  9. ↑ a b c BW Ray: The crystal structure of Zunyite . In: PhD at the California Institute of Technology Pasadena, California . 1956, p. 1–197 ( rruff.info [PDF; 12.8 MB ; accessed on April 24, 2020]).
  10. ^ A b c S. John Louisnathan, GV Gibbs: Aluminum-silicon distribution in Zunyite . In: American Mineralogist . tape 57 , 1972, p. 1089–1108 ( rruff.info [PDF; 1.3 MB ; accessed on April 24, 2020]).
  11. ↑ a b c d Werner H. Baur, Tsutomu Ohta: The Si 5 O 16 pentamer in Zunyite refined and empirical relations for individual silicon-oxygen bonds . In: Acta Crystallographica . B38, 1982, p. 390–401 ( Brief description and link to the PDF file from scripts.iucr.org [accessed April 24, 2020]).
  12. ↑ a b c Peter J. Dirken, Arno PM Kentgens, Gerda H. Nachtegaal, AD MJ van der Eerden, J. Ben H. Jansen: Solid-state MAS NMR study of pentameric aluminosilicate groups with 180 ° interterrahedral Al-O-Si angles in Zunyite and harkerite . In: The American Mineralogist . tape 80 , 1995, pp. 39–45 ( minsocam.org [PDF; 605 kB ; accessed on April 24, 2020]).
  13. ↑ a b Bing Zhou, Barbara L. Sherriff, Francis Taulelle, Gang Wu: Nuclear magnetic resonance study of Al: Si and F: OH or in Zunyite . In: The Canadian Mineralogist . tape 41 , 2003, p. 891–903 ( rruff.info [PDF; 396 kB ; accessed on April 24, 2020]).
  14. ↑ Alain Baumer, Hubert Gimenez, Raoul Caruba, Guy Turco: Remplacements de regroupements atomiques dans la structure Zunyite . In: Bulletin de la Société Française de Minéralogie et de Cristallographie . tape 97 , 1974, pp. 271–277 ( rruff.info [PDF; 510 kB ; accessed on April 24, 2020]).
  15. ^ Giuseppe Giuseppetti, Fiorenzo Mazzi and Carla Tadini: The crystal structure of Harkenite . In: The American Mineralogist . tape 62 , 1977, pp. 263–272 ( minsocam.org [PDF; 993 kB ; accessed on April 24, 2020]).
  16. ↑ Ramiza K. Rastsvetaeva, AE Zadov and NV Chukanov: Crystal structure of Low-Symmetry Rondorfite . In: Crystallography Reports . tape 53 , 2008, p. 199–205 , doi : 10.1134 / S1063774508020065 ( researchgate.net [PDF; 396 kB ; accessed on April 24, 2020]).
  17. ↑ AC Kunwar, AR Thompson, HSGutowsky and Eric Oldfield: Solid State Aluminum-27 NMR Studies of Tridecameric Al-Ox Hydroxy Clusters in Basic Aluminum Selenate, Sulfate, and the Mineral Zunyite . In: Journal of Magnetic Resonance . tape 60 , 1984, pp. 467-472 ( citeseerx.ist.psu.edu [PDF; 490 kB ; accessed on April 24, 2020]).
  18. ↑ Localities for Zunyite. In: mindat.org. Hudson Institute of Mineralogy, accessed April 24, 2020 .
  19. ↑ Find location list for Zunyite at the Mineralienatlas and at Mindat , accessed on April 24, 2020.