Wendwilsonite

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Wendwilsonite
Wendwilsonite-zr18a.jpg
General and classification
other names

IMA 1985-047

chemical formula Ca 2 Mg [AsO 4 ] 2 • 2H 2 O
Mineral class
(and possibly department) 		Phosphates, arsenates and vanadates
System no. to Strunz
and to Dana 		8.CG.10 ( 8th edition : VII / C.17)
02/40/03/04
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  = 5.81  Å ; b  = 12.91 Å; c  = 5.62 Å
β  = 107.4 °
Formula units Z  = 2
Frequent crystal faces {011}, {111}, {010}, {110}
Twinning after {100}
Physical Properties
Mohs hardness 3 to 4
Density (g / cm 3 ) measured: 3.52 (8); calculated: 3.57
Cleavage completely after {010}
Break ; Tenacity uneven
colour light pink to rose red
Line color light pink
transparency transparent to translucent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.694
n β  = 1.703
n γ  = 1.713
Birefringence δ = 0.019
Optical character biaxial positive
Axis angle 2V = 87 ° (measured), 88 ° (calculated)

Wendwilsonite is a very rare mineral from the mineral class of "phosphates, arsenates and vanadates". It crystallizes in the monoclinic crystal system with the idealized chemical composition Ca 2 Mg [AsO 4 ] 2 · 2H 2 O and is therefore chemically a water-containing calcium - magnesium arsenate.

Wendwilsonite is the magnesium analogue of Roselith (Ca 2 Co [AsO 4 ] 2 · 2H 2 O) and forms a complete mixed crystal row with it . In naturally grown wendwilsonite crystals, a small amount of magnesium is therefore usually represented by cobalt ( substitution , diadochy), which is expressed in the formula with element symbols in round brackets: Ca 2 (Mg, Co) [AsO 4 ] 2 · 2H 2 O

The mineral usually develops prismatic crystals up to about six millimeters in length, stretched along the a-axis, with a glass-like sheen on the surfaces. The color of the transparent to translucent crystals varies, depending on the amount of cobalt added, between light and dark pink to rose red and becomes darker the more magnesium is replaced by cobalt.

Etymology and history

Wendwilsonite was first discovered in the mining district of Bou Azer (formerly Bou Azzer) about 30 kilometers east of Taznakht in the province of Ouarzazate (Souss-Massa-Draâ region) in Morocco and in the Sterling mine near Sterling Hill about one kilometer west of Ogdensburg in the US State of New Jersey .

The mineral was first described in 1987 by Pete J. Dunn , Bozidar Darko Sturman and Joseph A. Nelen , who named it after the author and editor of the " Mineralogical Record " Wendell E. Wilson in honor of his contributions to mineralogy.

Type material of the mineral is stored in the Royal Ontario Museum in Toronto, Canada (Catalog No. M42119) and the National Museum of Natural History in Washington, DC, USA (Catalog No. 136288).

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the wendwilsonite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "water-containing phosphates without foreign anions ", where it, together with brandtite , cassidyite , Roselith-β ( Roselith-Beta ), Collinsite , Fairfieldite , Gaitite , Hillite , Messelite , Parabrandtite , Roselith , Talmessite and zinc roselite form the "Fairfieldite-Roselith Group" with the system no. VII / C.17 formed.

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 assigns wendwilsonite to the category of “phosphates etc. without additional anions; with H 2 O “. However, this is further subdivided according to, so that the mineral is classified according to its composition in the sub-section “With large and medium-sized cations; RO 4  : H 2 O = 1: 1 "can be found, where only together with brandtite, roselite and zinc roselite the" roselite group "with the system no. 8.CG.10 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns wendwilsonite to the class of "phosphates, arsenates and vanadates" and there in the department of "water-containing phosphates etc.". Here it is in the " Roselith subgroup (Monoclinic: P21 / c) " with system no. 02/40/03 within the subsection “Water-containing phosphates etc., with A 2+ (B 2+ ) 2 (XO 4 ) × x (H 2 O)”.

Crystal structure

Wendwilsonite crystallizes monoclinically in the space group P 2 1 / c (space group no. 14) with the lattice parameters a  = 5.81  Å ; b  = 12.91 Å; c  = 5.62 Å and β = 107.4 ° and two formula units per unit cell . Template: room group / 14

Education and Locations

Wendwilsonite from the Aghbar Mine, Aghbar, Bou Azer, Morocco (field of view 4 mm)

Wendwilsonite forms as a secondary mineral in cobalt-containing hydrothermal mineral deposits .

In addition to its Moroccan type locality Bou Azer (Aghbar mine and opencast mine, corridor No. 2), where the mineral occurred in paragenesis with talmessite and erythrin , and its American type locality Sterling Mine, the mineral has so far only been found in cobalt iron - Dashkasan deposit in the Daşkəsən (Rayon) Rayon Daşkəsən of Azerbaijan, the Mina Torrecillas in the Salar Grande district in the Chilean province of El Tamarugal (formerly Iquique province , Región de Tarapacá ) as well as on the Hartkoppe (Fuchs quarry) in the Lower Franconian district of Schneeberg in the Saxon Ore Mountains in Germany.

See also

literature

  • Pete J. Dunn, B. Darko Sturman, Joseph A. Nelen: Wendwilsonite, the Mg analogue of roselite, from Morocco, New Jersey, and Mexico, and new data on roselite. In: American Mineralogist Volume 72 (1987), pp. 217–221 ( PDF 507.2 kB )
  • Uwe Kolitsch , Michel Fleck: Third update on compounds with kröhnkite-type chains: the crystal structure of wendwilsonite [Ca 2 Mg (AsO 4 ) 2 · 2H 2 O] and the new triclinic structure of synthetic AgSc (CrO 4 ) 2 · 2H 2 O and M 2 Cu (Cr 2 O 7 ) 2 · 2H 2 O (M = Rb, Cs). In: European Journal of Mineralogy. Volume 18 (2006), pp. 471-482 doi : 10.1127 / 0935-1221 / 2006 / 0018-0471
  • Ray L. Frost, Ricardo Scholz, Andrés López, Fernanda Maria Belotti, Yunfei Xi: Structural characterization and vibrational spectroscopy of the arsenate mineral wendwilsonite. In: Spectrochimica Acta Part A-Molecular and Biomolecular Spectroscopy. Volume 118 (2014), pp. 737-743 doi : 10.1016 / j.saa.2013.09.048

Web links

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

Individual evidence

  1. ↑ a b c IMA / CNMNC List of Mineral Names; September 2015 (PDF 1.5 MB)
  2. ↑ a b c d 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.  484 .
  3. ↑ a b c d e f g Wendwilsonite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 65, 2 kB )
  4. ↑ a b c d e Mindat - Wendwilsonite
  5. ^ Homepage of the Mineralogical Record
  6. ↑ Find location list for Wendwilsonite at the Mineralienatlas and at Mindat