Wilhelmkleinit

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Wilhelmkleinit
Wilhelmkleinite.jpg
Wilhelmkleinit from the Tsumeb Mine, Namibia
General and classification
other names

IMA 1997-034

chemical formula
  • ZnFe 3+ 2 (AsO 4 ) 2 (OH) 2
  • ZnFe 3+ 2 [(OH) 2 | (AsO 4 ) 2 ]
Mineral class
(and possibly department) 		Phosphates, arsenates and vanadates
System no. to Strunz
and to Dana 		8.BB.40 ( 8th edition : VII / B.08)
05.41.19.01
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group P 2 1 / c (No. 14)Template: room group / 14
Lattice parameters a  = 6.631  Å ; b  = 7.611 Å; c  = 7.377 Å
β  = 91.80 °
Formula units Z  = 2
Frequent crystal faces {100}, {430}, {31 1 }
Twinning Penetration twins according to {101}
Physical Properties
Mohs hardness 4.5
Density (g / cm 3 ) 4,364 (calculated)
Cleavage Split surfaces parallel (23 2 )
Break ; Tenacity uneven; not specified
colour blackish green
Line color green
transparency translucent
shine matt, diamond luster on fractured surfaces
Crystal optics
Refractive index n  = 1.94
Optical character biaxial
Pleochroism strong from olive green to emerald green to reddish brown

Wilhelmkleinite is a very rarely occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the monoclinic crystal system with the chemical composition ZnFe 3+ 2 [(OH) 2 | (AsO 4 ) 2 ] and is therefore chemically a water-containing zinc - iron - arsenate with additional hydroxide ions (OH - ).

Wilhelmkleinit develops spear-shaped crystals up to 5 mm in size, which come together to form aggregates , grew up as the most recent formation of aluminum-rich scorodite and are accompanied by gerdtremmelite and adamin .

Etymology and history

The American mineral dealer Charles Locke Key is considered the discoverer of Wilhelmkleinite, who noticed the blackish green crystals on two scorodite specimens from the Tsumeb mine bought in Tsumeb in 1994 and who made this mineral available to the authors of the type publication for identification. Corresponding investigations led to the determination of the presence of a new mineral, which was recognized by the International Mineralogical Association (IMA) in 1997 and described as Wilhelmkleinite in 1999 by a German research team including Jochen Schlüter , Karl-Heinz Klaska , Karen Friese , Gunadi Adiwidjaja and Georg Gebhard . The mineral was named after Wilhelm Klein (1889–1939), manager (manager) of the OMEG deposits in Namibia from 1916 to 1939. Wilhelm Klein put together the first systematic mineral collection of the Tsumeb mine, which is now part of the holdings of the Harvard Mineralogical Museum from Harvard University , Cambridge , Massachusetts , USA . Wilhelm Klein discovered an unknown mineral that was first described by Pufahl as germanite in 1922 .

Type material of the mineral is kept in the Mineralogical Museum of the University of Hamburg in Germany (holotype, collection no. MMHH TS 291, in the safe of the museum).

classification

In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , Wilhelmkleinite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the division of "anhydrous phosphates, with foreign anions F, Cl, O, OH", where he together with Barbosalith , Hentschelit , Lazulith , Lipscombit , Richellit , Scorzalith , Trolleit and Zinklipscombit the " Lazulite group" with the system no. VII / B.08 .

The 9th edition of Strunz's mineral systematics, which has been in force since 2001 and is used by the International Mineralogical Association (IMA), also assigns Wilhelmkleinite to the category 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 other anions (OH etc.) to the phosphate, arsenate or vanadate complex (RO 4 ), so that the mineral is classified in the sub-section “With only medium-sized Cations; (OH etc.): RO 4  ≤ 1: 1 ”can be found, where together with Barbosalith, Hentschelite, Lazulite and Scorzalith the“ Lazulite group ”with the system no. 8.BB.40 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Wilhelmkleinit to the class of "phosphates, arsenates and vanadates" and there in the department of "water-containing phosphates etc.". Here he is the only member of the unnamed group May 41, 2019 within the subdivision of " Anhydrous phosphates etc., with hydroxyl or halogen with (AB) 2 (XO 4 ) Z q ".

Chemism

Wilhelmkleinit has (assuming As = 2 and O = 10) the measured composition Zn 0.84 Fe 3+ 2.07 (AsO 4 ) 2 O 2 H 3.2 , resulting in ZnFe 3+ 2 (AsO 4 ) 2 (OH) 2 has been idealized and requires levels of 16.65% ZnO, 32.66% Fe 2 O 3 , 47.01% As 2 O 5 and 3.68% H 2 O.

Wilhelmkleinite is the analogue of water-containing ojuelaite, free of water of crystallization .

Crystal structure

Wilhelmkleinite crystallizes in the monoclinic crystal system in the space group P 2 1 / c (space group no. 14) with the lattice parameters a  = 6.631  Å ; b  = 7.611 Å; c  = 7.377 Å and β = 91.80 ° and two formula units per unit cell . Template: room group / 14

The crystal structure of Wilhelmkleinits consists of deformed [AsO 4 ] 3- - tetrahedra , [FeO 6 ] 9- - octahedra and [ZnO 6 ] 10- octahedra. Two of the oxygen atoms of the [AsO 4 ] 3− tetrahedra form common corners with the [FeO 6 ] 9− octahedra, while the other two atoms each have one [FeO 6 ] 9− and one [ZnO 6 ] 10− Octahedron and in this way represent points in which the three coordination polyhedra are connected to each other. Furthermore, the two octahedron variants have common corners, which creates a three-dimensional structure.

properties

Drawing of an idealized Wilhelmkleinite twin from the Tsumeb mine

morphology

Wilhelmkleinit forms spear-shaped, relatively small-area crystals up to 5 mm in size, in which only the surface forms {100}, {430} and {31 1 } have been identified. The crystal form that determines the costume is the prism {430}. Penetration twins according to {101} are very typical (cf. the adjacent figure). The closely intergrown crystals form aggregates up to 1 × 1 × 0.5 cm in size.

physical and chemical properties

The Wilhelmkleinite crystals are blackish green , the line color is described as green. The surfaces of the translucent crystals are matt, but the fracture surfaces have a diamond-like sheen .

The mineral has split surfaces parallel (23 2 ). With a Mohs hardness of 4.5, Wilhelmkleinite is one of the medium-hard minerals that are somewhat easier to scratch with a pocket knife than the reference mineral apatite . The calculated density is 4.364 g / cm³. Wilhelmkleinit does not fluoresce in the long or short-wave UV range.

Education and Locations

As of 2016, Wilhelmkleinite could only be described as a very rare mineral formation by its type locality , the world-famous Cu-Pb-Zn-Ag-Ge-Cd deposit of the "Tsumeb Mine" (Tsumcorp Mine) in Tsumeb , Oshikoto region , Namibia where Wilhelmkleinit was first found on the 44th level at a depth of 1500 m. He found himself grown up on two levels with light blue, aluminum-rich scorodite and is accompanied by tiny tan-colored gerdtremmelite crystals, maximum 0.5 mm in size, and yellow adamin. Wilhelmkleinit is a typical secondary mineral and formed in the third oxidation zone in dolomite stones seated hydrothermal polymetallic ore deposit Tsumeb from the sulfidic and arsenidischen Primärerzmineralen.

use

Due to its rarity, Wilhelmkleinite is only of interest to mineral collectors.

See also

literature

  • Gunadi Adiwidjaja, Karen Friese, Karl-Heinz Klaska, Paul B. Moore, Jochen Schlüter (2000): The crystal structure of the new mineral wilhelmkleinite ZnFe 3+ 2 (OH) 2 (AsO 4 ) 2 . In: Journal of Crystallography. Volume 215, pp. 96-101 ( PDF, 460 kB ).
  • John L. Jambor, Nikolai N. Pertsev, Andrew C. Roberts (1999): New Mineral Names. In: American Mineralogist. Volume 84, p. 1197 ( PDF, 36 kB ).
  • Jochen Schlüter, Karl-Heinz Klaska, Karen Friese, Gunadi Adiwidjaja, Georg Gebhard (1998): Wilhelmkleinite, ZnFe 3+ 2 (AsO 4 ) 2 (OH) 2 , a new mineral from Tsumeb, Namibia. In: New Yearbook Mineralogy, monthly books. Volume 1998 (Issue 12), pp. 558-564.
  • Wilhelmkleinit. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America. 2001 ( PDF; 64 kB ).

Web links

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

Individual evidence

  1. ↑ a b c d e f g h i j k l m n o p q r s t Jochen Schlüter, Karl-Heinz Klaska, Karen Friese, Gunadi Adiwidjaja, Georg Gebhard: Wilhelmkleinite, ZnFe 3+ 2 (AsO 4 ) 2 ( OH) 2 , a new mineral from Tsumeb, Namibia. In: New Yearbook Mineralogy, monthly books. Volume 1998 (Issue 12), pp. 558-564.
  2. ↑ a b Wilhelmkleinit. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America. 2001 ( PDF; 64 kB ).
  3. ↑ a b c d Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  445 .
  4. ↑ a b Joseph Anthony Mandarino : Abstracts of new mineral descriptions. In: Mineralogical Record. 2000, Volume 31 (Issue 2), pp. 205-206.
  5. ^ Type mineral catalog Germany - storage of the holotype stage Wilhelmkleinit
  6. ↑ Gunadi Adiwidjaja, Karen Friese, Karl-Heinz Klaska, Paul B. Moore, Jochen Schlüter (2000): The crystal structure of the new mineral wilhelmkleinite ZnFe 3+ 2 (OH) 2 (AsO 4 ) 2 . In: Journal of Crystallography. 2000, Volume 215, pp. 96-101 ( PDF; 460 kB ).
  7. ↑ Mindat - number of locations for Wilhelmkleinit
  8. ↑ Find location list for Wilhelmkleinit at the Mineralienatlas and at Mindat