Quenstedtite
| Quenstedtite | |
|---|---|
 |
|
| General and classification | |
| other names | |
| chemical formula | Fe 3+ 2 [SO 4 ] 3 • (9 + 2) H 2 O |
|
Mineral class (and possibly department) |
Sulfates |
|
System no. to Strunz and to Dana |
7.CB.65 ( 8th edition : VI / C.08) 08/29/05/01 |
| Crystallographic Data | |
| Crystal system | triclinic |
| Crystal class ; symbol | triclinic pinacoidal; 1 |
| Space group | P 1 (No. 2) |
| Lattice parameters |
a = 6.18 Å ; b = 23.60 Å; c = 6.54 Å α = 94.2 °; β = 101.7 °; γ = 96.3 ° |
| Formula units | Z = 2 |
| Twinning | after {010} |
| Physical Properties | |
| Mohs hardness | 2.5 |
| Density (g / cm 3 ) | measured: 2.11 to 2.15; calculated: 2.14 |
| Cleavage | perfect after {010}, good after {100} |
| Break ; Tenacity | fibrous; brittle |
| colour | light purple to reddish purple; colorless to pink in transmitted light |
| Line color | White |
| transparency | transparent |
| shine | weak glass gloss, silk gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.547 n β = 1.566 n γ = 1.594 |
| Birefringence | δ = 0.047 |
| Optical character | biaxial positive |
| Axis angle | 2V = 70 ° (measured), 82 ° (calculated) |
| Other properties | |
| Chemical behavior | easily soluble in water |
Quenstedtite is a seldom occurring mineral from the mineral class of "sulfates (selenates, tellurates, chromates, molybdates and tungstates)" with the chemical composition Fe 3+ 2 [SO 4 ] 3 · (9 + 2) H 2 O or simplified Fe 3 + 2 (SO 4 ) 3 · 11H 2 O or Fe 3+ 2 (SO 4 ) 3 · 10–11H 2 O. Chemically speaking, quenstedtite is thus a hydrous iron (III) sulfate or, better, the decahydrate of iron (III) -sulfate.
Quenstedtite crystallizes in the triclinic crystal system and develops transparent, tabular to short prismatic crystals up to about five millimeters in length and a glass-like gloss on the surfaces. Most of the time, the mineral is found in the form of translucent, crusty coatings and granular mineral aggregates that shimmer more like silk .
The color of quenstedtite varies between light purple and reddish purple, but also appears colorless to pink in transmitted light . His line color , however, is always white.
Etymology and history
From a study trip through Chile , which in 1883 also led to the area around Tierra Amarilla in the province of Copiapó belonging to the Región de Atacama , Gustav Steinmann brought, among other things, some Coquimbit grades, which he left to the Mineralogical Institute of the University of Strasbourg .
Gottlob Eduard Linck then discovered previously unknown, millimeter-sized crystals of reddish-purple color and tabular habit . He described the newly discovered mineral in 1888 in his contribution to the knowledge of the sulfates of Tierra amarilla near Copiapó in Chile and named it after the geologist, palaeontologist, mineralogist and crystallographer Friedrich August Quenstedt .
The type material of the mineral is kept in the Mines ParisTech (also École nationale supérieure des mines de Paris ) in Paris .
classification
Already in the outdated, but partly still in use, 8th edition of the mineral classification according to Strunz , the quenstedtite belonged to the mineral class of "sulfates, chromates, molybdates, tungstates" (including some selenates and tellurates) and there to the department of "water-containing sulfates, without foreign anions ", Where together with alunogen , coquimbit , kornelite , lausenite , meta-alunogen , paracoquimbit and rhomboclase he created the" rhomboclase-coquimbit group "with the system no. VI / C.08 .
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 classifies quenstedtite in the category of "sulfates (selenates, etc.) without additional anions, with H 2 O". However, this is further subdivided according to the relative size of the cations involved , so that the mineral can be found according to its composition in the sub-section “With only medium-sized cations”, where the “Quenstedtite group” with the system no. 7.CB.65 and the other member Munakatait .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns quenstedtite to the class of "sulfates (and relatives)" and there in the department of "water-containing acids and sulfates". Here he is to be found as the only member of the unnamed group 08/29/05 within the sub-section “ Hydrous acids and sulfates with (A) 2 (XO 4 ) 3 × x (H 2 O)”.
Chemism
In chemically pure form, quenstedtite (Fe 3+ 2 [SO 4 ] 3 · (9 + 2) H 2 O) contains 10 parts of water 41.41% SO 3 , 27.53% Fe 2 O 3 and 31.06% H 2 O. With 12 parts water, 40.16% SO 3 , 26.70% Fe 2 O 3 and 33.14% H 2 O are contained accordingly .
In the case of naturally occurring quenstedtites, the analyzes also showed small amounts of calcium in the form of CaO of 0.4% and traces of MgO .
Crystal structure
Quenstedtite crystallizes triclinically in the space group P 1 (space group no. 2) with the lattice parameters a = 6.18 Å ; b = 23.60 Å; c = 6.54 Å; α = 94.2 °; β = 101.7 ° and γ = 96.3 ° as well as two formula units per unit cell .
properties
With a Mohs hardness of 2.5, quenstedtite is on the border between soft and medium-hard minerals. It can no longer be scratched with a fingernail like the reference mineral gypsum (hardness 2), but more easily than the reference mineral calcite (hardness 3) with a copper coin.
The mineral shows perfect cleavage according to the plane of symmetry {010} and a less perfect, but good cleavage according to the orthopinacoid {100}. In contrast , its tendency to break is more fibrous and similar to that of plaster of paris .
Quenstedtite dissolves very easily in water and turns the resulting thick, oily liquid yellowish. According to its first description, this liquid should have a bitter, astringent taste. With water loss, Quenstedit transforms into Coquimbit over time. Mineral samples must therefore be kept in sealed containers for preservation.
Education and Locations
Quenstedtite forms in the oxidation zone of pyrite-rich deposits under dry climatic conditions . In addition to the weathering product coquimbite, copiapite and romanite can also occur as accompanying minerals .
As a rare mineral formation, quenstedtite could only be detected at a few sites, whereby so far (as of 2018) fewer than 20 sites have been documented. In addition to its type locality in Tierra Amarilla in the Región de Atacama , the mineral was also found in Chile in the former copper mines of Barranca del Sulfato on the Mejillones peninsula , the Alcaparrosa mine on Cerro Alcaparrosa mountain about 3 km southwest of the Cerritos Bayos train station near Calama and the Queténa mine in the Chuquicamata copper deposit in the Antofagasta region .
In Germany, the mineral is known from the Richelsdorfer Hütte in the mountains of the same name in the Hersfeld-Rotenburg district of Hesse, the copper mines near Marsberg in the Hochsauerland district of North Rhine-Westphalia and from the Friedrichssegen mine in the Rhein-Lahn district of Rhineland-Palatinate.
Other previously known sites include the hydro-sulphate tunnel near Plaka in the Lavrio mining district in the Greek region of Attica , the fumaroles over burning coal from Ikushunbetsu near Mikasa on the Japanese island of Hokkaidō, the Venus silver mine on the Windy Arm River about 17 km south of Carcross in Canadian Yukon territory, the Sântimbru-Băi mercury deposit in the Romanian Harghita district , the Maximilianschacht near Banská Štiavnica (German Schemnitz ) in Slovakia and the Sulfur Hole (German sulfur hole ) near the ghost town of Calico in California and an unnamed site near Montpelier in Muscatine County , Iowa in the United States.
See also
literature
- G. Linck: Contribution to the knowledge of the sulfates of Tierra Amarilla near Copiapó in Chile. (Communications from the Mineralogical Institute of the University of Strasbourg, No. 11) . In: P. Groth (Ed.): Journal for crystallography and mineralogy . tape 15 . Verlag von Wilhelm Engelmann, Leipzig 1889, p. 1–28 ( available online at archive.org - Internet Archive - Quenstedtit from p. 11).
- Jimmy N. Thomas, Paul D. Robinson, Jen H. Fang: Crystal structures and mineral chemistry of hydrated ferric sulfates. IV. The crystal structure of quenstedtite . In: American Mineralogist . tape 59 , 1974, pp. 582-586 ( rruff.info [PDF; 624 kB ; accessed on July 8, 2018]).
- C. Doelter, H. Leitmeier (Ed.): Sulphates, Chromium, Molybdenum, Wolfram, Uranium, Haloid Salts and Salt Deposits: Volume IV Part Two . Springer, Berlin, Heidelberg 1929, p. 552 ( limited preview in Google Book Search - Unchanged reprint 2013 under ISBN 978-3-642-49871-8 ).
Web links
- Mineral Atlas: Quenstedtite (Wiki)
- Webmineral - Quenstedtite (English)
- American-Mineralogist-Crystal-Structure-Database - Quenstedtite (English)
Individual evidence
- ↑ 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. 385 (English).
- ↑ a b c d e f Quenstedtite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 67 kB ; accessed on July 8, 2018]).
- ↑ a b c d e f Mindat - Quenstedtite (English)
- ^ IMA / CNMNC List of Mineral Names; March 2018 (PDF 1.65 MB; English)
- ↑ G. Linck: Contribution to the knowledge of the sulfates of Tierra Amarilla near Copiapó in Chile. (Communications from the Mineralogical Institute of the University of Strasbourg, No. 11) . In: P. Groth (Ed.): Journal for crystallography and mineralogy . tape 15 . Verlag von Wilhelm Engelmann, Leipzig 1889, p. 11 ( available online at archive.org - Internet Archive ).
- ↑ G. Linck: Contribution to the knowledge of the sulfates of Tierra Amarilla near Copiapó in Chile. (Communications from the Mineralogical Institute of the University of Strasbourg, No. 11) . In: P. Groth (Ed.): Journal for crystallography and mineralogy . tape 15 . Verlag von Wilhelm Engelmann, Leipzig 1889, p. 3 ( available online at archive.org - Internet Archive ).
- ↑ a b c G. Linck: Contribution to the knowledge of the sulfates of Tierra Amarilla near Copiapó in Chile. (Communications from the Mineralogical Institute of the University of Strasbourg, No. 11) . In: P. Groth (Ed.): Journal for crystallography and mineralogy . tape 15 . Verlag von Wilhelm Engelmann, Leipzig 1889, p. 12 ( available online at archive.org - Internet Archive ).
- ↑ Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 .
- ↑ a b List of locations for quenstedtite in the Mineralienatlas and Mindat