Wadeit

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Wadeit
Wadeite-744671.jpg
Tabular, light purple wadeit crystals on orthoclase (white) and aegirin (black) from Eweslogtschorr , Chibinen , Kola peninsula, Russia (size: 2.7 cm × 2.7 cm × 2.2 cm)
General and classification
chemical formula K 2 Zr [Si 3 O 9 ]
Mineral class
(and possibly department)
Silicates and Germanates
System no. to Strunz
and to Dana
9.CA.10 ( 8th edition : VIII / E.01)
59.01.01.04
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol hexagonal dipyramidal; 6 / m
Space group P 6 3 / m (No. 176)Template: room group / 176
Lattice parameters a  = 6.9360  Å ; c  = 10.1822 Å
Formula units Z  = 2
Physical Properties
Mohs hardness 6 to 6.5
Density (g / cm 3 ) measured: 3.10 to 3.13; calculated: 3.16
Cleavage indistinct
Break ; Tenacity shell-like
colour colorless, pale pink to violet, light brown
Line color White
transparency transparent
shine Diamond luster
Crystal optics
Refractive indices n ω  = 1.625
n ε  = 1.655
Birefringence δ = 0.030
Optical character uniaxial positive
Other properties
Special features Cathodoluminescence

Wadeit is a seldom occurring mineral from the mineral class of "silicates and germanates" with the chemical composition K 2 Zr [Si 3 O 9 ] and thus chemically a potassium - zirconium - silicate . Structurally, Wadeit belongs to the ring silicates .

Wadeit crystallizes in the hexagonal crystal system and develops tabular to prismatic crystals with a diamond-like sheen on the surfaces. The crystals are generally up to about five millimeters in size, but crystals with a diameter of up to three centimeters have also been discovered at Yukspor in Russia. In its pure form, Wadeit is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline formation, it can also appear white and take on a pale pink to violet or light brown color due to foreign admixtures. His line color , however, is always white.

Etymology and history

The mineral in investigating was first discovered leucite - Lamproiten of the Wolgidee Hills from the region Kimberley of the state of Western Australia . The study was carried out by Arthur Wade and Rex T. Prider between 1937 and 1938 in the Department of Mineralogy and Petrology in Cambridge . Leucite-containing rocks were found in a number of isolated volcanic holes, nineteen of which were examined and mapped by Arthur Wade (1878-1951).

The mineral was first described in 1939 by Rex T. Prider, who named it Wadeit in honor of Arthur Wade. Wade was responsible for collecting the row of rocks and discovered the new Wolgidee Hills intrusion in which Wadeit was found.

The type material (holotype) is available from the University of Western Australia in Perth under catalog no. Saved in 18760 .

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the Wadeit belonged to the mineral class of "silicates and germanates" and there to the department of "ring silicates (cyclosilicates)", where together with Bazirit , Benitoit , Bobtraillit , Pabstit and Rogermitchellit the "Benitoitgruppe" with the system no. VIII / E.01 .

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also classifies Wadeit in the "ring silicates" section. This is, however, further subdivided according to the structure of the rings and the possible presence of additional anions , so that the mineral according to its structure and its composition in the subdivision "[Si 3 O 9 ] 6− triple single rings without island-like, complex anions" is where it is the only member of the unnamed group 9.CA.10 .

The systematics of minerals according to Dana , which is predominantly used in the English-speaking world , assigns the Wadeit to the more finely subdivided division of "ring silicates: triple rings". Here it can be found alongside bazirite, benitoite and pabstit as the fourth mineral in the “benitoite group” 59.01.01 within the sub-section “ ring silicates: anhydrous triple rings, no other anions ”.

Chemism

The idealized, theoretical composition of Wadeit (K 2 Zr [Si 3 O 9 ]) consists of 19.66% potassium (K), 22.94% zirconium (Zr), 21.19% silicon (Si) and 36.21 % Oxygen (O).

The chemical analysis of the samples from the type locality of the mineral (Wolgidee Hills, Western Australia) showed, however, additional small additions of titanium in the form of 1.58% TiO 2 as well as traces of Al 2 O 3 , Fe 2 O 3 , MgO and SrO .

Crystal structure

Wadeit crystallizes hexagonally in the space group P 6 3 / m (space group no. 176) with the lattice parameters a  = 6.9360  Å and c  = 10.1822 Å as well as two formula units per unit cell . Template: room group / 176

As a ring silicate , the crystal structure of Wadeit, like that of Benitoit, consists of [Si 3 O 9 ] 6- triple single rings. The basic building block of silicate Anionenkomplexes thus consists of three SiO 4 - tetrahedra , which via shared oxygen ions to simple rings are connected. Simple here means that these three-ring rings are isolated in the structure, that is, not directly, but are linked to one another at the corners via intermediate layers of [ZrO 6 ] octahedra by shared oxygen ions. In contrast to benitoite, the silicate rings in the Wadeit are not placed on top of each other in the direction of the c-axis, but alternately occupy different positions between the zirconium octahedra. The potassium atoms are embedded in the offset gaps between the silica rings and the zirconium octahedra .

properties

With a Mohs hardness of 6 to 6.5, Wadeit is one of the hard minerals that, like the reference mineral orthoclase (hardness 6), can just be scratched with a steel file. Its density is measured between 3.10 and 3.13 g / cm 3 and calculated 3.16 g / cm 3 . The mineral is insoluble even in hot acids.

Wadeit shows cathodoluminescence , so it can be made to glow by bombarding it with electrons .

Education and Locations

Wadeit (pale pink) with aegirin (black needles) and feldspar (white) from Eweslogtschorr, Russia (field of view 3 cm)

Wadeit formed as an ancillary part in leucite, volcanic rocks and in carbonatite - veins and nepheline - syenite - pegmatites .

As a rare mineral formation, Wadeit could only be proven in a few places, whereby around 30 sites have been documented worldwide. At its type locality, the Wolgidee Hills near the municipality of Noonkanbah, as well as at other sites in the vicinity of Fitzroy Crossing and the Ellendale diamond mines in Derby-West Kimberley Shire , apatite , barite , calcite , chalcedony and titanium appeared as accompanying minerals in addition to leucite - and potassium-containing fluorine richterite , olivine , perovskite , phlogopite and zeolite . Another well-known site in Western Australia is the Argyle diamond mine near the lake of the same name in the Wyndham-East Kimberley Shire .

Abundant finds of Wadeit were also known on the Kola Peninsula in the Russian Oblast of Murmansk , more precisely on various mountains in the Chibinen such as Koaschwa , Eweslogchorr , Kukiswumtschorr , Raswumtschorr and Yukspor .

The only other known site in Europe so far is, besides the Kola peninsula, the former Minas Del Carmen mine near the village of La Celia and the eroded volcano of the same name in the province of Murcia with apatite-rich rock.

Other well-known sites are among others in North America

in South America

  • the Bortolan alkali quarry near Poços de Caldas in the Brazilian state of Minas Gerais

in South Africa

and in Asia

See also

literature

  • Rex T. Prider: Some minerals from the leucite-rich rocks of the West Kimberley area, Western Australia . In: Mineralogical Magazine . tape 25 , 1939, pp. 373–387 (English, rruff.info [PDF; 666 kB ; accessed on February 4, 2019]).
  • JP Marble, WF Foshag: New mineral names . In: American Mineralogist . tape 25 , 1940, p. 253–254 (English, rruff.info [PDF; 143 kB ; accessed on February 4, 2019]).

Web links

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

Individual evidence

  1. ^ A b c 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.  595-596 (English).
  2. a b David Barthelmy: Wadeit Mineral Data. In: webmineral.com. Retrieved February 3, 2019 .
  3. a b Hongwu Xu, Alexandra Navrotsky, M. Lou. Balmer, Yali Su: Crystal-chemical and energetic systematics of wadeite-type phases A 2 BSi 3 O 9 (A = K, Cs; B = Si, Ti, Zr) . In: Physics and Chemistry of Minerals . tape 32 , no. 5 , September 2005, p. 426-435 , doi : 10.1007 / s00269-005-0017-2 (English, []).
  4. a b c d e f g h Wadeite . 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; 72  kB ; accessed on February 3, 2019]).
  5. 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 .
  6. a b c d e Wadeite. In: mindat.org. Hudson Institute of Mineralogy, accessed February 3, 2019 .
  7. ^ A b 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. 1223 .
  8. Rex T. Prider: Some minerals from the leucite-rich rocks of the West Kimberley area, Western Australia . In: Mineralogical Magazine . tape 25 , 1939, pp. 373–387 (English, rruff.info [PDF; 666 kB ; accessed on February 4, 2019]).
  9. Catalog of Type Mineral Specimens - W. (PDF 52 kB) In: docs.wixstatic.com. Commission on Museums (IMA), December 12, 2018, accessed August 29, 2019 .
  10. Localities for Wadeite. In: mindat.org. Hudson Institute of Mineralogy, accessed February 3, 2019 .
  11. List of locations for Wadeit in the Mineralienatlas and Mindat