Ranciéit

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Ranciéit
Rancieite-320245.jpg
4.3 cm × 4.3 cm large, massive aggregate with light brown ranciéit
General and classification
chemical formula (Ca, Mn 2+ ) 2+ (Mn 3.5 4+ O 8 ) • 3H 2 O
Mineral class
(and possibly department) 		Oxides and hydroxides
System no. to Strunz
and to Dana 		4.FL.40 ( 8th edition : IV / D.12)
07.10.01.01
Similar minerals Takanelite
Crystallographic Data
Crystal system trigonal
Crystal class ; symbol trigonal-rhombohedral; 3
Space group P 3 (No. 147)Template: room group / 147
Lattice parameters a  = 2.845  Å ; c  = 7.485 Å
Formula units Z  = 1
Physical Properties
Mohs hardness 2.5 to 3
Density (g / cm 3 ) measured: 3.336
Cleavage is missing
colour black, dark to light brown, purple
Line color dark brown
transparency opaque, transparent in thin fragments
shine Metallic luster

Ranciéit is a rather rare mineral from the mineral class of " oxides and hydroxides " with the chemical formula (Ca, Mn 2+ ) 2+ (Mn 3.5 4+ O 8 ) · 3H 2 O.

Ranciéit crystallizes in the trigonal crystal system and forms thin lamellae, polycrystalline mineral aggregates , as well as stalactites and incrustations of black, brown or purple in color.

Etymology and history

Ranciéit was found in 1857 by the French mineralogist Alexandre Félix Gustave Achille Leymérie in the type locality , the Rancié mine near Sem in the Ariège department ( France ). It is named after this too.

classification

In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the ranciéit belonged to the mineral class of "oxides and hydroxides" and there to the department of "oxides with the molar ratio of metal: oxygen = 1: 2", where it together with takanelite formed the unnamed group IV / D.12 .

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 Ranciéit to the class of "oxides and hydroxides", but there in the department of "hydroxides (without V or U ) " a. This section is further subdivided according to the possible presence of crystal water in the compound and the crystal structure, so that the mineral according to its composition and structure is classified in the sub-section “Hydroxides with H 2 O ± (OH); Layers of edge-linked octahedra “can be found, where it forms the unnamed group 4.FL.40 together with takanelite .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the ranciéit to the class of "oxides and hydroxides" and there in the department of "multiple oxides". Here you can also find takanelite in the unnamed group 07.10.01 within the subdivision of " Multiple Oxides ".

Crystal structure

Ranciéit crystallizes in the trigonal crystal system in the space group P 3 (space group number 147) with the lattice parameters a = 2.845  Å and c = 7.485 Å and one formula unit per unit cell .

Modifications and varieties

Ranciéit forms a series of minerals with takanelite in which calcium is replaced by manganese.

Education and Locations

Ranciéit from the Siresol mine, Vajo Siresol, Montecchio, municipality of Negrar , Veneto, Italy (size: 2.2 cm × 3.3 cm × 2 cm)
Birnessite / Ranciéit pseudomorphism, presumably based on Serandite from the Demix-Varennes mine, Saint-Amable, Québec , Canada. The olive green "hedgehogs" consist of aegirine (very typical for this locality). A few small, colorless droplets of strong green fluorescent opal can be seen on the white microclink crystals.

Ranciéit is formed by weathering in manganese deposits , mostly in limestone or limestone caves. It is associated with todorokite , calcite and limonite .

As a rather rare mineral formation, Ranciéit could only be detected at a few sites, whereby so far (as of 2016) around 150 sites are known. Besides its type locality "Le Rancié Mine" in Midi-Pyrenees, the mineral in France occurred even at Lembach in the Bas-Rhin and in several places of the Haut-Rhin in Alsace, in the municipality Esmoulières in Franche-Comté and the Lozère and several places in the Pyrénées-Orientales department .

In Germany, ranciéit was mainly found in the Spessart in Bavaria; in the Harz from Lower Saxony to Thuringia; in the Eifel from North Rhine-Westphalia to Rhineland-Palatinate; in Siegerland in North Rhine-Westphalia; near Nothweiler in Rhineland-Palatinate and near Wolkenstein in the Saxon Ore Mountains.

In Austria, the mineral appeared at Badersdorf in Burgenland, in several places in Carinthia and Styria and at Lend in Salzburg, and in Switzerland it has been used by Frick AG and Holderbank AG in the canton of Aargau and in Tinizong-Rona in the canton of Graubünden found.

Other sites are in Australia , Bulgaria , China , Greece , Indonesia , Italy , Japan , Canada , the Canary Islands , Cuba , Mexico , Norway , Poland , Romania , Russia , Slovakia , Spain , South Africa , Turkey , Ukraine , Hungary and the United States of America (USA).

See also

List of minerals

literature

Web links

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

Individual evidence

  1. ^ A b 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.  245 .
  2. ↑ a b c d Andreas Ertl, Franz Pertlik, Markus Prem, Jeffrey E. Post, Soo Jin Kim, Franz Brandstätter, Ralf Schuster: Rancíeite crystals from Friesach, Carinthia, Austria. In: European Journal of Mineralogy. 2005, 17, 1, pp. 163-172, doi : 10.1127 / 0935-1221 / 2005 / 0017-0163 .
  3. ^ Mindat - Ranciéite
  4. ↑ Ranciéite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 71 kB )
  5. ^ Mindat - Ranciéite-Takanelite Series
  6. ↑ Mindat - Number of locations for Ranciéit
  7. ↑ Find location list for Ranciéit in the Mineralienatlas and Mindat