Tschermigit

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Tschermigit
Tschermigit (Ammonalaun) - Tschermig, Böhmen.jpg
Tschermigit, discovery site Tschermig / Bohemia .
General and classification
chemical formula
  • (NH 4 ) Al (SO 4 ) 2 • 12H 2 O
  • NH 4 Al [SO 4 ] 2 • 12H 2 O
Mineral class
(and possibly department) 		Sulphate containing water
System no. to Strunz
and to Dana 		07.CC.20 ( 8th edition : VI / C.14)
05/29/05/03
Crystallographic Data
Crystal system cubic
Crystal class ; symbol cubic-disdodecahedral; 2 / m  3
Space group Pa 3 (No. 205)Template: room group / 205
Lattice parameters a  = 12.24  Å
Formula units Z  = 4
Physical Properties
Mohs hardness 1.5
Density (g / cm 3 ) measured: 1.645; calculated: 1.641
Cleavage completely after {100}
Break ; Tenacity shell-like
colour colorless to white
Line color White
transparency transparent
shine Silk gloss, glass gloss
Crystal optics
Refractive index n  = 1.485
Birefringence none, as it is optically isotropic
Other properties
Chemical behavior easily soluble in water; bitter, astringent taste

Tschermigit , also known as ammonium alum , is a seldom occurring mineral from the mineral class of sulfates ( and relatives ) with the chemical composition NH 4 Al [SO 4 ] 2 · 12H 2 O and thus, chemically speaking, aluminum alum .

Tschermigit crystallizes in the cubic crystal system and is usually found in the form of white efflorescence or fibrous to stalky aggregates with a silk-like sheen on the surfaces. Pronounced crystals are rare, but then can reach a size of about one centimeter. The surfaces of the transparent and colorless to white crystals have a glass luster. With a Mohs hardness of 1.5, Tschermigit lies between the reference minerals talc (1) and gypsum (2), so it can be easily scratched with a fingernail.

Etymology and history

Tschermigit was first discovered near the town of Čermníky in the Czech region of Bohemia . The first description was in 1853 by Franz von Kobell , who named the mineral after its type locality or its German name "Tschermig" (also Tschermich ).

The Čermníky site no longer exists as the village had to give way to the Nechranice reservoir .

classification

In the outdated 8th edition of the mineral classification according to Strunz , the Tschermigit belonged to the mineral class of "sulfates, chromates, molybdates, wolframates" (including some selenates and tellurates) and there to the department of "hydrous sulfates without foreign anions ", where it belongs together with alum - (K) (formerly potash alum ) and alum (N) (formerly soda alum ) as well as in the appendix with voltaite the "alum group" with the system no. VI / C.08 .

In the Lapis mineral directory according to Stefan Weiß, which, out of consideration for private collectors and institutional collections, is still based on this old form of Karl Hugo Strunz's system , the mineral was given the system and mineral number. VI / C.14-30 . In the "Lapis Classification" This also corresponds to the department "hydrous sulphates without foreign anions" where Tschermigite along with alum (K), alum (Na), Ammoniomagnesiovoltait , Lanmuchangit , Lonecreekit , Pertlikit , Voltait and Zincovoltait an independent, but unnamed group forms (as of 2018).

The 9th edition of Strunz's mineral systematics, which has been valid since 2001 and was last updated in 2009 by the International Mineralogical Association (IMA) , classifies the Tschermigit in the category of "Sulphates (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 medium-sized and large cations”, where together with Lanmuchangite, Lonecreekite, Alaun- (K) and Alaun- (N) the "alum group" with the system no. 07.CC.20 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , also assigns the Tschermigit to the class of "sulfates, chromates and molybdates" and there in the category of "water-containing acids and sulfates". Here, too, Tschermigit is a member of the alum group with system no. 05/29/05 and the other members Alaun- (K), Alaun- (Na), Lonecreekit and Lanmuchangit can be found in the subdivision of " Hydrous acids and sulphates with AB (XO 4 ) 2 × x (H 2 O) ".

Crystal structure

Tschermigit crystallizes in the cubic crystal system in the space group Pa 3 (space group no. 205) with the lattice parameter a  = 12.24  Å and 4 formula units per unit cell . Template: room group / 205

properties

Tschermigit, like the other alums, is easily soluble in water (192 g / l at 25 ° C). For this reason, Tschermigit is not stable and the crystals can dissolve even at high ambient humidity . Mineral samples should therefore always be kept in airtight containers. Above about 93 ° C it gives off its crystal water, where it then dissolves in it. The aqueous solutions have a salty-bitter, astringent taste.

Education and Locations

Tschermigit forms as efflorescence on burning coal heaps or on the edges of fumaroles . Due to the high solubility in water, the separation takes place exclusively from the gas phase and under very dry ambient conditions. Crystal formations from oversaturated solutions are not yet known in nature. Accompanying minerals include plaster of paris , ammonium jarosite , epsomite , rostite , alunogen , boussingaultite , mascagnin and voltaite .

As a rare mineral formation, Tschermigite could only be detected at a few sites. So far (as of 2011) around 60 sites are known. In addition to its type locality Čermníky, the mineral occurred in the Czech Republic in several places in Bohemia such as Kladno , Mnichovo Hradiště and Sušice . It was also found in the Moravian communities of Zastávka and Žeravice .

In Germany, Tschermigit has so far been found in the Clara mine near Oberwolfach in Baden-Württemberg, the Anna mine near Alsdorf in North Rhine-Westphalia, the Queen Carola mine (also Paul Berndt mine) near Freital in Saxony and on the now closed sedimentation dump of the Lichtenberg opencast mine Ronneburg uranium mining area found in Thuringia.

In Switzerland, the mineral has so far only been found at Brissago TI in Ticino and Collonges VS in the canton of Valais.

Other locations are among others in Brazil, China, the Democratic Republic of the Congo, France, Italy, Japan, Poland, Portugal, Russia, Slovakia, Spain, South Africa, Tajikistan, Hungary and the United States of America (USA).

use

Tschermigit does not form any mineable deposits. For this reason it has no meaning as a mineral for the production of aluminum or aluminum salts. Known uses are of historical interest only .

Due to its astringent effect , Tschermigit, like other alums , can be used as a deodorant or razor stick . In English, Tschermigit is also known as Deodorant Stone .

Manipulations and imitations

Due to the ease with which synthetic alum crystals can be produced, they are often offered as Tschermigit. It should be noted that naturally formed Tschermigite crystals are small and usually not very well defined. Furthermore, natural Tschermigit is white, while synthetic alums have intense green, blue or purple hues.

See also

literature

  • Franz von Kobell : Tables for determining the minerals by means of simple chemical experiments on dry and wet routes . 6th, increased edition. Joseph Lindauer'sche Buchhandlung, Munich 1858, p. 47 , 2. They are soluble in hydrochloric acid, some also in water, without noticeable residue. The edition does not form a jelly. Tschermigit (ammonia alum ) ( rruff.info [PDF; 91 kB ; accessed on June 9, 2020]).

Web links

Commons : Tschermigite  - Collection of images, videos and audio files

Individual evidence

  1. ↑ Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: March 2020. (PDF; 2.44 MB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, March 2020, accessed June 9, 2020 .
  2. ↑ 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.  388 .
  3. ↑ a b c d e Tschermigite . 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; 66  kB ; accessed on June 9, 2020]).
  4. ↑ a b c David Barthelmy: Tschermigite Mineral Data. In: webmineral.com. Retrieved June 9, 2020 .
  5. ^ François Sulpice Beudant : Traité élémentaire de Minéralogie . tape  2 . Verdière, Paris 1832, p. 497 (French, available online at gallica.bnf.fr [accessed June 9, 2020]).
  6. ↑ Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
  7. ↑ Ernest H. Nickel , Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF; 1.82 MB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed June 9, 2020 .
  8. ↑ Mindat - Number of localities for Tschermigit
  9. ↑ Find location list for Tschermigit at the Mineralienatlas and at Mindat , accessed on June 9, 2020.