Thometzekit
| Thometzekit | |
|---|---|
 |
|
| General and classification | |
| other names |
IMA 1982-103 |
| chemical formula |
|
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.CG.15 ( 8th edition : VII / C.31) 02/40/09/03 |
| Similar minerals | Gartrellit |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | C 2 / m (No. 12) |
| Lattice parameters |
a = 9.08 Å ; b = 6.30 Å; c = 7.66 Å β = 117.0 ° |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 4 to 5 |
| Density (g / cm 3 ) | calculated: 5.21 |
| Cleavage | Please complete |
| colour | bluish green to green, greenish yellow, light gray |
| Line color | White |
| transparency | translucent |
| shine | earthy matt |
| Crystal optics | |
| Refractive indices |
n α = 1.850 n β = 1.870 n γ = 1.920 |
| Birefringence | δ = 0.070 |
| Optical character | biaxial positive |
| Axis angle | 2V = 70 ° (measured), 68 ° (calculated) |
Thometzekit is a rarely occurring mineral from the mineral class of "phosphates, arsenates and vanadates" with the idealized chemical composition PbCu 2+ 2 [AsO 4 ] 2 · 2H 2 O and is therefore chemically a water-containing lead - copper - arsenate . Since part of the copper in naturally occurring Thometzekites can be replaced (substituted) by zinc , the formula is in various sources with Pb (Cu, Zn) 2 [AsO 4 , SO 4 ] 2 · 2 (H 2 O, OH) or also indicated with Pb (Cu, Zn) 2 [H 2 O | AsO 4 ] 2 .
Thometzekit crystallizes in the monoclinic crystal system , but develops only tiny, platelet-shaped to wedge-shaped crystals about 20 μm long and one μm thick. It is mostly found in the form of crusty coatings on other minerals. Thometzekit is translucent and from bluish-green to green or greenish-yellow to light-gray color and has an earthy matt appearance in crusts. Occasionally, Thometzekit samples can also have a waxy sheen . Thometzekit leaves a white line on the marking board . With a Mohs hardness of 4 to 5, Thometzekit is one of the medium-hard minerals that, like the reference minerals fluorite (hardness 4) and apatite (hardness 5), can be easily or just scratched with a pocket knife .
Thometzekit can easily be confused with Gartrellit because of its similarity in terms of color and material .
Etymology and history
Thometzekit was first discovered in the well-known "Tsumeb Mine" (also Tsumcorp Mine ) near the town of the same name in the Namibian region of Oshikoto ( Otjikoto ). It was first described in 1985 by Karl Schmetzer, Bernhard Nuber and Olaf Medenbach, who named the mineral after the former general director of the Tsumeb mining company Wilhelm Thometzek.
The type material of the mineral is stored in the mineralogical-petrological institute of the University of Heidelberg under the catalog no. HT: 10'11'19 ' (two samples) kept.
classification
Already in the outdated but still partially in use 8th edition of the mineral classification by Strunz of Thometzekit belonged to the mineral class of "phosphates, arsenates and vanadates" and then to the department "Water-containing phosphates without foreign anions" where he along with Cabalzarit , Cobaltlotharmeyerit , Cobalttsumcorit , Ferrilotharmeyerit , Gartrellit , Helmutwinklerit , Krettnichit , Lotharmeyerit , Lukrahnit , Manganlotharmeyerit , Mawbyit , Mounanait , Nickellotharmeyerit , Nickelschneebergit , Phosphogartrellit , Rappoldit , Schneebergit , Tsumcorit and Zinkgartrellit the "Tsumcorit-Gartrellit group" with the system number. VII / C.31 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 the Thometzekit to the section “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 the phosphate, arsenate or vanadate complex (RO 4 ) to the proportion of water of crystallization , so that the mineral can be classified in the sub-section “With large and medium-sized cations; RO 4 : H 2 O = 1: 1 "is to be found, where it is only together with Cabalzarite, Cobaltlotharmeyerite, Cobalt Sumcorite, Ferrilotharmeyerite, Krettnichite, Lotharmeyerit, Manganlotharmeyerit, Mawbyit, Mounanaite, Nickellotharmeyerit, Nickelschneebergit, Schneecorbergite and Tsorcorbergite" with the system no. 8.CG.15 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Thometzekit to the class of "phosphates, arsenates and vanadates" and there in the department of "water-containing phosphates etc.". Here it is in the " Helmutwinklerite subgroup " with the system no. 02/40/09 within the subsection “Phosphates containing water, etc., with A 2+ (B 2+ ) 2 (XO 4 ) × x (H 2 O)”.
Chemism
Six microprobe analyzes showed an average composition of 36.04% PbO , 0.18% CaO , 19.18% CuO , 5.63% ZnO , 0.30% FeO , 33.13% As 2 O 5 , 0.06% SiO 2 and 4.9% H 2 O (determined by thermogravimetric analysis ). The thermogravimetric loss occurs in a range between 350 and 500 ° C. The data obtained correspond to the idealized formula Pb (Cu, Zn) 2 (AsO 4 ) · 2H 2 O with Cu> Zn. The idealized zinc-free end link with the formula PbCu 2 [AsO 4 ] · 2H 2 O contains 34.44% PbO , 24.54% CuO, 35.46% As 2 O 5 and 5.56% H 2 O (all data in% by weight).
Crystal structure
Thometzekit crystallizes monoclinically in the space group C 2 / m (space group no. 12) with the lattice parameters a = 9.08 Å ; b = 6.30 Å; c = 7.66 Å and β = 117.0 ° as well as two formula units per unit cell .
Education and Locations
Thometzekit formed secondarily in the oxidation zone of hydrothermally formed polymetallic ores - deposits in dolomite rocks . Anglesite , mimetesite and gypsum appear as accompanying minerals .
As a rare mineral formation, Thometzekit could only be detected at a few sites, whereby so far (as of 2018) a little more than 10 sites have been documented. Its type locality Tsumeb Mine is the only known site in Namibia to date .
In Germany, the mineral was only found in the Clara mine near Oberwolfach and in the Lisbühl tunnels west of Todtnau in Baden-Württemberg, in the Wildermann mine near Müsen (Siegen-Wittgenstein district) in North Rhine-Westphalia and near Zinnwald-Georgenfeld in the district Saxon Switzerland-Eastern Ore Mountains to be discovered.
Other previously known sites are the Les Montmins pit (Sainte Barbe filon) in the municipality of Echassières in the French department of Allier , the mining district Lavrio ( Laurion ) in the Greek region of Attica, Dalnegorsk in the Russian region of Primorye, Moldava (German Moldau ) in the Czech region Ústecký kraj region and the Gold Hill Mine near Gold Hill in the Deep Creek Mountains in Tooele County of the US state of Utah.
use
Due to its rarity, Thometzekit is only of interest to mineral collectors.
See also
literature
- Karl Schmetzer, Bernhard Nuber, Olaf Medenbach: Thometzekite, a new mineral from Tsumeb, Namibia, and symmetry relations in the tsumcorite-helmutwinklerite family . In: New yearbook for mineralogy, monthly books . tape 85 , no. 10 , 1985, pp. 446-452 .
- John L. Jambor, Kenneth W. Bladh, T. Scott Ercit, Joel D. Grice, Edward S. Grew: New Mineral Names . In: American Mineralogist . tape 73 , 1988, pp. 927-935 ( rruff.info [PDF; 879 kB ; accessed on May 21, 2018]).
- Werner Krause, Klaus Belendorff, Heinz-Jürgen Bernhardt, Catherine A. McCammon, Herta Effenberger, Werner Mikenda: Crystal chemistry of the tsumcorite-group minerals. New data on ferrilotharmeyerite, tsumcorite, thometzekite, mounanaite, helmutwinklerite, and a redefinition of gartrellite . In: European Journal of Mineralogy . tape 10 , no. 2 , 1998, p. 179-206 , doi : 10.1127 / ejm / 10/2/0179 .
- Ray L. Frost, Matt Weier: Raman and infrared spectroscopy of tsumcorite mineral group . In: New yearbook for mineralogy, monthly books . tape 7 , 2004, p. 317–336 , doi : 10.1127 / 0028-3649 / 2004 / 2004-0317 .
Web links
- Mineral Atlas: Thometzekit (Wiki)
- RRUFF Database-of-Raman-spectroscopy - Thometzekite (English)
- American-Mineralogist-Crystal-Structure-Database - Thometzekite (English)
Individual evidence
- ↑ a b c IMA / CNMNC List of Mineral Names; March 2018 (PDF 1.65 MB)
- ↑ a b c Stefan Weiss: The large Lapis mineral directory. All minerals from A - Z and their properties . 6th completely revised and supplemented edition. Weise, Munich 2014, ISBN 978-3-921656-80-8 .
- ↑ 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. 485 .
- ↑ Webmineral - Thometzekite (English)
- ↑ a b Thometzekite . 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; 65 kB ; accessed on May 17, 2018]).
- ↑ a b c d e f g Mindat - Thometzekite (English)
- ^ A b John L. Jambor, Kenneth W. Bladh, T. Scott Ercit, Joel D. Grice, Edward S. Grew: New Mineral Names . In: American Mineralogist . tape 73 , 1988, pp. 927-935 ( rruff.info [PDF; 879 kB ; accessed on May 21, 2018] Thometzekit from p. 5).
- ↑ Catalog of Type Mineral Specimens - T. (PDF 87 kB) In: docs.wixstatic.com. Commission on Museums (IMA), December 12, 2018, accessed August 29, 2019 .
- ↑ Mineralienatlas: Thometzekit
- ↑ Find location list for Thometzekit in the Mineralienatlas and Mindat