Botryogen

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Botryogen
Botryogen mineralogical museum bonn.jpg
Botryogen crystals from Knoxville, CA / USA
General and classification
chemical formula MgFe 3+ [OH | (SO 4 ) 2 ] • 7H 2 O
Mineral class
(and possibly department) 		Please complete!
System no. to Strunz
and to Dana 		7.DC.25 ( 8th edition : VI / D.10)
09/31/06/01
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic 2 / m
Space group P 2 1 / n
Lattice parameters a  = 10.51  Å ; b  = 17.85 Å; c  = 7.14 Å
β  = 100.00 °
Formula units Z  = 4
Physical Properties
Mohs hardness 2 to 2.5
Density (g / cm 3 ) 2.14 to 2.23
Cleavage perfect after {010}, good after {110}
Break ; Tenacity shell-like
colour Orange red
Line color yellow
transparency transparent to translucent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.522
n β  = 1.529
n γ  = 1.577
Birefringence δ = 0.055
Optical character biaxial positive
Axis angle 2V = 42 °
Pleochroism visible: X = yellow; Y = light red; Z = orange red

Botryogen is a rather seldom occurring mineral from the mineral class of "sulphates, selenates, tellurates, chromates, molybdates and tungstates", more precisely a hydrous magnesium - iron - sulphate with the chemical composition MgFe 3+ [OH | (SO 4 ) 2 ] • 7H 2 O.

Botryogen crystallizes in the monoclinic crystal system and develops mostly prismatic, striped crystals of orange-red color, the crystal surfaces of which have a glass luster. But it is also found in grape-like and radial-radial mineral aggregates .

Etymology and history

Botryogen was first described in 1815 by Jöns Jakob Berzelius , who derived it from the Greek words βότρυς for grape and γευυăυ for carry , meaning "grape-carrying" in relation to the grape and stalactic forms of training that were found in the type locality Falun in Sweden.

classification

In the old (8th edition) and the new systematics of minerals according to Strunz (9th edition) , the botryogen belongs to the division of "Water-containing sulfates with foreign anions ". Since the 9th edition of Strunz's mineral classification, this department has been more precisely divided according to the size of the cations involved and the crystal structure. The mineral can therefore now be found in the subsection “with medium-sized cations and chains of edge-sharing octahedra ”.

The systematics of minerals according to Dana also assigns the botryogen to the class of sulfates (and related compounds), but there in the department of " hydrated sulfates with hydroxyl or halogen with the general formula (A + B 2+ ) (XO 4 ) Z q  • x (H 2 O) ".

Education and Locations

Botryogen is a typical secondary mineral that is formed by oxidation from pyrite in arid climatic conditions .

So far, the mineral has been found at 38 sites (status: 2009), namely La Alcaparrosa ( San Juan ) in Argentina; Mount Isa in Australia; the regions of Antofagasta and Tarapacá in Chile; Charbes in the French canton of Villé ; Rammelsberg and Ronneburg (Thuringia) in Germany; Haji Abbad in the Iranian province of Hormozgan ; the Italian regions of Liguria , Piedmont and Tuscany ; Shikoku in Japan; Sillian in Austria; Falun in Sweden; Smolník in Slovakia ; Minas de Riotinto in Spain; Balaklava in Ukraine; Rudabánya and Cserhát in the northern Hungarian Central Mountains ; and in Arizona , California , Nevada , Ohio , Pennsylvania , Tennessee, and Utah in the United States .

Crystal structure

Botryogen crystallizes in the monoclinic crystal system in the space group P 2 1 / n with the lattice parameters a = 10.51  Å , b = 17.85 Å, c = 7.14 Å and β = 100.00 ° as well as four formula units per unit cell .

See also

Individual evidence

  1. ↑ a b c d Webmineral - Botryogen (English)
  2. ↑ a b American Mineralogist Crystal Structure Database - Botryogen (English, 1967)
  3. ↑ a b c botryogen at mindat.org (engl.)
  4. ↑ Mindat - Localities for Botryogen
  5. ↑ American Mineralogist Crystal Structure Database - Botryogen (English, 1967)

literature

Web links

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