Talmessite
| Talmessite | |
|---|---|
 |
|
| General and classification | |
| 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.05 ( 8th edition : VII / C.17) 02/40/02/05 |
| Crystallographic Data | |
| Crystal system | triclinic |
| Crystal class ; symbol | triclinic pinacoidal; 1 |
| Room group (no.) | P 1 (No. 2) |
| Lattice parameters |
a = 5.87 Å ; b = 6.94 Å; c = 5.54 Å, α = 97.3 °; β = 108.7 °; γ = 108.1 ° |
| Formula units | Z = 1 |
| Physical Properties | |
| Mohs hardness | 5 |
| Density (g / cm 3 ) | measured: 3.421; calculated: [3.53] |
| Cleavage | no |
| colour | colorless, white, rose-red to brownish-pink, light green |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.672 n β = 1.685 n γ = 1.698 |
| Birefringence | δ = 0.026 |
| Optical character | biaxial negative |
| Axis angle | 2V = 90 ° (measured); 88 ° (calculated) |
Talmessite is a rarely occurring mineral from the mineral class of "phosphates, arsenates and vanadates". It crystallizes in the triclinic crystal system with the idealized chemical composition Ca 2 Mg [AsO 4 ] 2 · 2H 2 O, so from a chemical point of view it is a water-containing calcium - magnesium - arsenate .
Talmessite only develops small crystals up to about three millimeters in size with a glass-like sheen on the surfaces. It is mostly found in radial, fibrous mineral aggregates , stalactitic forms or crusty coatings. In its pure form, Talmessite is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline formation, it can also appear white and, due to the addition of cobalt, it can take on a pinkish- red to brownish-pink or nickel a light green color, the transparency decreasing accordingly.
Talmessite forms a mixed crystal row with gaitite (Ca 2 Zn [AsO 4 ] 2 · 2H 2 O) and Roselite-β (Ca 2 Co [AsO 4 ] 2 · 2H 2 O).
Etymology and history
Talmessite was first discovered in the Talmessi mine near Anarak in the Iranian province of Isfahan and described in 1960 by P. Bariand and P. Herpin, who named the mineral after its type of locality .
Type material of the mineral is kept in the collection of Mines ParisTech in Paris (France) and Natural History Museum in London (England).
classification
Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the talmessite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "water-containing phosphates without foreign anions ", where together with brandtite , cassidyite , Collinsite , Fairfieldite , Gaitite , Hillite , Messelite , Parabrandtite , Roselith , Roselith-β ( Roselith-Beta ), Wendwilsonite and Zinc Roselite make up the "Fairfieldite-Roselith Group" with 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 talmessite to the category of “phosphates etc. without additional anions; with H 2 O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of phosphate, arsenate or vanadate complex to the proportion of water of crystallization , so that the mineral is classified in the sub-section “With large and medium-sized cations; RO 4 : H 2 O = 1: 1 "is to be found, where together with Roselith-β, Cassidyite, Collinsite, Fairfieldite, Gaitite, Hillite, Messelite, Nickeltalmesit (IMA 2008-051) and Parabrandtit the" Fairfieldite group "is found System no. 8.CG.05 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the talmessite to the class of "phosphates, arsenates and vanadates" and there in the department of "water-containing phosphates etc.". Here it is also in the " Fairfieldite subgroup (Triklin: P 1 ) " with the system no. 40.02.02 to be found in the subsection "Water-containing phosphates etc., with A 2+ (B 2+ ) 2 (XO 4 ) × x (H 2 O)".
Education and Locations
Talmessite forms secondarily in the oxidation zone of hydrothermal deposits . As accompanying minerals may include Annabergit , aragonite , Austinit , barite , calcite , dolomite , Domeykit , Erythrite , fluorite , Gaitit , Pikropharmakolith and Pharmakolith occur.
As a rare mineral formation, talmessite could only be detected at a few sites, with around 50 sites known to date (as of 2014). Its type locality Talmessi Mine near Anarak is the only known site in Iran to date.
In Germany, Talmessit has so far been able to be found at Wittichen in Baden-Württemberg, in the Wilhelm mine near Bauhaus (Nentershausen) and on an ore dump near Richelsdorf in Hesse, as well as in shaft 139 (Abrahamhalde) near Lauta (Marienberg) , in shaft 366 neha Bad Schlema - Hartenstein and can be found near Schneeberg in the Saxon Ore Mountains.
The only known site in Austria so far is Hirschentor, where the mineral was discovered during a road outcrop near Klippitztörl in Carinthia.
In Switzerland, the mineral is known so far only from the Falotta mine near Tinizong-Rona in the canton of Graubünden.
Other locations are in Afghanistan, Chile, France, Greece, Italy, Japan, Morocco, Namibia, the Czech Republic, Hungary, the United Kingdom (UK) and the United States of America.
Crystal structure
Talmessite crystallizes triclinically in the space group P 1 (space group no. 2) with the lattice parameters a = 5.87 Å ; b = 6.94 Å; c = 5.54 Å; α = 97.3 °; β = 108.7 ° and γ = 108.1 ° and one formula unit per unit cell .
See also
literature
- P. Bariand, P. Herpin: Un arseniate de calcium et de magnésium, isomorphic de la β rosélite. In: Bulletin de la Société Française de Minéralogie et de Cristallographie. Volume 83, 1960, pp. 118–121 ( rruff.info PDF; 1.86 MB; French)
- Michael Fleischer : New mineral names. In: American Mineralogist. Volume 45, 1960, pp. 1313-1317 ( rruff.info PDF; 374 kB; Talmessit from p. 3)
- Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 645 (first edition: 1891).
Web links
- Mineral Atlas: Talmessite (Wiki)
- Webmineral - Talmessite.
- Database of Raman spectroscopy - Talmessite.
- American Mineralogist Crystal Structure Database - Talmessite.
Individual evidence
- ↑ a b Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 5th completely revised and supplemented edition. Weise, Munich 2008, ISBN 978-3-921656-70-9 .
- ↑ a b c d e 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. 483 .
- ↑ a b Talmessite. 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; 67 kB).
- ↑ a b c d Mindat - Talmessite.
- ↑ Mindat - Number of localities for Talmessite.
- ↑ location list for the Talmessit Mineralienatlas and Mindat .