Yvonite

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Yvonite
Yvonite-115679.jpg
Yvonit from the type locality "Salsigne" pit, France (field of view 4 mm)
General and classification
other names

IMA 1995-012

chemical formula Cu [AsO 3 OH] • 2H 2 O
Mineral class
(and possibly department) 		Phosphates, arsenates and vanadates
System no. to Strunz
and to Dana 		8.CB.25 ( 8th edition : VII / C.06)
39.01.10.01
Crystallographic Data
Crystal system triclinic
Crystal class ; symbol triclinic pinacoidal; 1
Space group P 1 (No. 2)Template: room group / 2
Lattice parameters a  = 7.63  Å ; b  = 11.17 Å; c  = 6.02 Å,
α  = 89.3 °; β  = 86.5 °; γ  = 74.4 °
Formula units Z  = 4
Physical Properties
Mohs hardness 3.5 to 4
Density (g / cm 3 ) measured: 3.20 (2); calculated: 3.22
Cleavage completely after {100}; indistinct after {010}
Break ; Tenacity uneven; brittle
colour turquoise blue
Line color blue
transparency transparent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.615
n β  = 1.660
n γ  = 1.700
Birefringence δ = 0.085
Optical character biaxial negative
Axis angle 2V = measured: 82 °; calculated: 84 °
Pleochroism weak: Z = blue, Y = light blue, X = light blue to colorless

Yvonite is a very rare mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the triclinic crystal system with the chemical composition Cu [AsO 3 OH] · 2H 2 O, so it is a water-containing copper arsenate.

Yvonit only develops small, tabular crystals up to about 0.15 millimeters in length, which are stretched along the c-axis and usually arranged in radial or spherical mineral aggregates . The crystals themselves are transparent and turquoise-blue in color and have a glass-like sheen on the surfaces , but due to the multicrystalline formation in aggregate forms the mineral appears more translucent to opaque. Yvonit also leaves a blue line on the marking board .

Etymology and history

Yvonit was first described in 1998 by Halil Sarp and Radovan Černý , who named the mineral after the Swiss professor of crystallography at the University of Geneva Klaus Yvon (* 1943).

Yvonit was discovered by MG Favreau in the "Salsigne" mine, which is located on the south side of the Montagne Noire and about 15 km north of Carcassonne in the French department of Aude .

The type material of the mineral is kept in the Natural History Museum of the City of Geneva .

classification

In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of Yvonit belonged to the department of "water containing phosphates without foreign anions " where he along with Chudobait , Geigerit , Geminit , Kobaltkoritnigit , Koritnigit , Lindackerit , Pushcharovskit , Rollandit , Slavkovit and Trichalcit the "Chudobait group" with the system no. VII / C.06 .

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 Yvonite to the category of “phosphates etc. without additional anions; with H 2 O “. However, this section is further subdivided according to the relative size of the cations involved and the molar ratio of the phosphate, arsenate or vanadate complex to the water of crystallization contained , so that the mineral according to its composition in the sub-section “With only medium-sized cations; RO 4  : H 2 O = 1: 1 “can be found, where it is the only member of the unnamed group 8.CB.25 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Yvonit to the class of "phosphates, arsenates and vanadates" and there in the department of "hydrous acidic phosphates etc.". Here he is to be found as the only member of the unnamed group 39.01.10 within the subdivision “ Hydrous acid phosphates etc., A + [HXO 4 ] × x (H 2 O)”.

Crystal structure

Yvonite crystallizes triclinically in the space group P 1 (space group no. 2) with the lattice parameters a  = 7.63  Å ; b  = 11.17 Å; c  = 6.02 Å; α = 89.3 °; β = 86.5 ° and γ = 74.4 ° as well as four formula units per unit cell .

The crystal structure consists of two independent, symmetrically distorted CuO 5 (H 2 O) octahedra , which are linked at one edge and form chains parallel to the c-axis. Two also independent, distorted ASO 3 (OH) tetrahedra link these chains to form layers parallel to the lattice plane 'a'. Between the layers there are two independent and symmetrically arranged H 2 O molecules, which are only weakly connected to one another via a network of hydrogen bridges. The weak bond between the layers is also the reason for the perfect cleavage of the mineral in this direction.

Education and Locations

Yvonite is a secondary mineral that forms on top of other minerals in the heaps of gold-bearing arsenic sulfide deposits . As accompanying minerals may include arsenopyrite dignified, bismuth , chalcopyrite , Geminit , Lindackerit and Pushcharovskit occur.

Apart from its type locality , the “Salsigne” mine near Carcassonne, the mineral in France could so far (as of 2013) only be found in the “Cap Garonne” mine near Le Pradet in the Var department. The only other known site to date is Jáchymov (German Sankt Joachimsthal ) in the Bohemian part of the Czech Ore Mountains.

use

Due to its rarity, Yvonite has no economic significance other than as a mineral sample, but is nevertheless a sought-after collector's mineral due to its appealing color.

See also

literature

  • Halil Sarp, Radovan Černý: Description and crystal structure of yvonite, Cu (AsO 3 OH) • 2H 2 O . In: American Mineralogist . tape 83 , 1998, pp. 383–389 ( minsocam.org [PDF; 204 kB ; accessed on May 28, 2018]).

Web links

Commons : Yvonite  - 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.  475 .
  2. ↑ Webmineral - Yvonite
  3. ↑ a b c Yvonite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 66  kB ; accessed on May 28, 2018]).
  4. ↑ a b c Mindat - Yvonite
  5. ↑ Find location list for Yvonit in the Mineralienatlas and Mindat