Thaumasite

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Thaumasite
Thaumasite-d06-80a.jpg
Thaumasite crystal specimen from the N'Chwaning II pit, Kuruman , Kalahari manganese field, North Cape, South Africa (size: 3.1 cm × 2.1 cm × 1.9 cm)
General and classification
chemical formula
  • Ca 3 Si (OH) 6 (CO 3 ) (SO 4 ) • 12H 2 O
  • Ca 6 Si 2 [6] [(OH) 12 | (CO 3 ) 2 (SO 4 ) 2 ] • 12H 2 O
Mineral class
(and possibly department)
Sulfates (including selenates, tellurates, chromates, molybdates, and tungstates)
System no. to Strunz
and to Dana
7.DG.15 ( 8th edition : VI / D.13)
April 32, 2004
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol hexagonal-pyramidal; 6th
Room group (no.) P 6 3 (No. 173)
Lattice parameters a  = 11.03  Å ; c  = 10.40 Å
Formula units Z  = 1
Physical Properties
Mohs hardness 3.5
Density (g / cm 3 ) measured: 1.877; calculated: [1.90]
Cleavage indistinct
Break ; Tenacity slightly mussel-like; brittle
colour colorless, white, light yellow
Line color White
transparency transparent to translucent
shine Glass gloss, matt, fat gloss, silk gloss
Crystal optics
Refractive indices n ω  = 1.507
n ε  = 1.468
Birefringence δ = 0.039
Optical character uniaxial negative

Thaumasite is a rather seldom occurring mineral from the mineral class of "sulfates (including selenates, tellurates, chromates, molybdates and tungstates)". It crystallizes in the hexagonal crystal system with the chemical composition Ca 6 Si 2 [6] [(OH) 12 | (CO 3 ) 2 (SO 4 ) 2 ] · 12H 2 O and is therefore a complex composition, hydrous calcium - silicon - sulfate with additional hydroxide and carbonate ions .

Thaumasite develops needle-like to prismatic crystals up to about five centimeters in length, but often occurs in the form of earthy, tangled needles or massive mineral aggregates or crusty coatings. In its pure form, thaumasite 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 foreign admixtures, take on a light yellow color, with the transparency decreasing accordingly.

Special properties

Some thaumasites show white fluorescence under UV light .

Etymology and history

Thaumasite was first discovered in the Bjelkes mines at Åreskutan (municipality of Åre ) in the Swedish province of Jämtlands län and described in 1878 by Adolf Erik Nordenskiöld (1832–1901), who named the mineral after the Greek word θαυμάζειν [thaumazein] for "to be amazed " or " be surprised ”named. Nordenskiöld chose the name based on the astonishing, because unusual, composition of the mineral of carbonate, sulfate and hexahydroxysilicate anions.

Type material of the mineral is stored at the University of Wroclaw (Polish: Uniwersytet Wrocławski ) in Poland (Catalog No. II-18500).

classification

In the outdated, but partly still in use, 8th edition of the mineral classification according to Strunz , the thaumasite belonged to the mineral class of "sulfates, chromates, molybdates and tungstates" and there to the department of "water-containing sulfates with foreign anions ", where together with bentorite , buryatite , Carrarait , Charlesit , Ettringit , Jouravskit and Sturmanit the "Ettringitgruppe" with the system no. VI / D.13 .

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 thaumasite in the category of "sulfates (selenates, etc.) with additional anions, with H 2 O". However, this is further subdivided according to the relative size of the cations involved and the type of other anion groups, so that the mineral is classified in the sub-section “With large to medium-sized cations; with NO 3 , CO 3 , B (OH) 4 , SiO 4 or IO 3 "is to be found, where together with bentorite, birunite , buryatite, carraraite , charlesite , ettringite, jouravskite and sturmanite the" ettringite group "with the system No. 7.DG.15 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the thaumasite to the class of "sulfates, chromates and molybdates" and there in the department of "composite sulfates". Here he is together with Carrarait, Charlesit , Jouravskit and Sturmanit in the " Charlesit group " with the system no. April 32, 2004 to be found in the subsection “ Compound sulfates (containing water) with polyanionic formula”.

Education and Locations

Pale yellow thaumasite with colorless calcite from the N'Chwaning II pit, South Africa (size: 3.3 cm × 2.7 cm × 2.3 cm)
White, fibrous-needle-like pectolite , overgrown with gray-white thaumasite from the Upper New Street Quarry (Burger's Quarry), Paterson (New Jersey) , USA (sample size 3 "× 2.5" × 2 "; corresponds to 7.62 cm × 6.35 cm × 5.08 cm)

Thaumasite forms in intramagmatic sulphide deposits , where it was usually deposited from hydrothermally drusen-forming . The accompanying minerals here include apophyllite , chalcopyrite ( copper pyrites ) and pyrite . Furthermore, thaumasite can arise secondarily in oxidation zones as a component of weathering crusts in loose tuffs as well as through contact metamorphosis in carbonate rocks and as a reaction product of geothermal water or salt water with basalts and tuffs. The accompanying minerals here include analcime , calcite , ettringite , gypsum , prehnite and various zeolites .

As a rather rare mineral formation, thaumasite can sometimes be abundant at various sites, but overall it is not very common. So far (as of 2014) around 180 sites for thaumasite are known. In addition to its type locality , the Bjelkes mines near Åreskutan in Jämtland, the mineral was also found in Sweden in various mines near Garpenberg in Dalarna , near Aitik and Kiruna in Lapland , near Åker in Södermanland and near Långban in Värmland .

The N'Chwaning pits near Kuruman in the Kalahari manganese field of South Africa, where rich crystal specimens with well-formed hexagonal-prismatic and water-clear thaumasites have been found, are known for their extraordinary thaumasite finds.

In Germany, thaumasite is known from various quarries near Steinach , Bötzingen and at Urenkopf near Haslach in the Kinzig valley in Baden-Württemberg; on the Zeilberg in Bavaria; on the Gaulsberg near Ortenberg in Hesse; at Adelebsen and Georgsmarienhütte in Lower Saxony; on several slag heaps near Eschweiler and Stolberg in the Rhineland, Kall in the Eifel, Letmathe in the Sauerland and Eiserfeld in the Siegerland in North Rhine-Westphalia, at many sites in the Rhineland-Palatinate Vulkaneifel ( Ettringen , Mendig ) as well as in the Kupferkammer-Hütte near Hettstedt in Saxony-Anhalt.

In Austria, the mineral was found on the Pauliberg near the Sankt Martin market in Burgenland, in the copper mines in the valley of the Großfragant near the municipality of Flattach in Carinthia, in a basalt quarry near Klöch and in some rock samples from the tunnel construction on the Galgenberg near Leoben in Styria.

Other locations include Australia, Bulgaria, China, France and French Polynesia, Israel, Italy, Japan, Jordan, Canada, Kazakhstan, Namibia, Norway, Poland, Romania, Russia, Slovakia, Spain, the Czech Republic, Uganda, Hungary, Uzbekistan, the United Kingdom (UK) and the United States of America (USA).


Crystal structure

Thaumasite crystallizes hexagonally in the space group P 6 3 (space group no. 173) with the lattice parameters a  = 11.03  Å and c  = 10.40 Å with one formula unit per unit cell .

use

Thaumasit- stage with greenish yellow, glass shiny crystals ( total size : 5.6 cm × 3.5 cm × 2.0 cm)

Thaumasite is of no importance for commercial use as a gem stone , despite its sometimes water-clear, shiny crystals, as it would scratch quickly when worn due to its low Mohs hardness of 3.5. For collectors, however, thaumasite is occasionally offered in different shapes .

See also

literature

  • Adolf Erik Nordenskiöld : Sur une nouvelle espèce minérale nommée thaumasite. In: Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences. Volume 87, 1878, pp. 313–314 ( PDF 185.2 kB , French)
  • RA Edge, HFW Taylor: Crystal structure of thaumasite, [Ca 3 Si (OH) 6 .12H 2 O] (SO 4 ) (CO 3 ). In: Acta Crystallographica Volume 27, 1971, pp. 594-601
  • Helmut Schrätze, Karl-Ludwig Weiner: Mineralogy. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 707 .
  • 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 , p. 460 .
  • GD Gatta, GJ McIntyre, JG Swanson, SD Jacobsen: Minerals in cement chemistry: A single-crystal neutron diffraction and Raman spectroscopic study of thaumasite, Ca 3 Si (OH) 6 (CO 3 ) (SO 4 ) 12H 2 O. In: American Mineralogist. Volume 97, 2012, pp. 1060-1069

Web links

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

Individual evidence

  1. ^ IMA / CNMNC List of Mineral Names; July 2014 (PDF 1.5 MB)
  2. 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.  410 .
  3. a b c Thaumasite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 72.7 kB )
  4. a b Mindat - Thaumasite
  5. ^ A b Walter Schumann: Precious stones and gemstones. All species and varieties in the world. 1600 unique pieces . 13th revised and expanded edition. BLV Verlags-GmbH., Munich et al. 2002, ISBN 3-405-16332-3 , p. 57, 232 .
  6. ^ A b Helmut Schrätze, Karl-Ludwig Weiner: Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 707 .
  7. Petr Korbel, Milan Novák: Mineral Encyclopedia . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 ( Dörfler Natur ).
  8. Mindat - Number of localities for Thaumasite
  9. List of sites for thaumasite in the Mineralienatlas and Mindat