Until

from Wikipedia, the free encyclopedia
Until
Bismite.jpg
General and classification
chemical formula Bi 2 O 3
Mineral class
(and possibly department)
Oxides and hydroxides
System no. to Strunz
and to Dana
4.CB.60 ( 8th edition : IV / C.02)
03/04/10/02
Similar minerals Sphaerobismoit
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic (pseudo-orthorhombic) 2 / m
Space group P 2 1 / c (No. 14)Template: room group / 14
Lattice parameters a  = 5.8486  Å ; b  = 8.1661 Å; c  = 7.5097 Å
β  = 113.00 °
Formula units Z  = 4
Physical Properties
Mohs hardness 4.5
Density (g / cm 3 ) 8.64 to 9.22
Cleavage is missing
Break ; Tenacity uneven
colour yellow, green-yellow, gray-green
Line color light yellow
transparency opaque, transparent to translucent only in very thin layers
shine weak diamond luster, matt, earthy
Crystal optics
Refractive index n  = 2.42
Birefringence δ = 0.000
Optical character biaxial

Bismit (also obsolete bismuth ocher ) is a mineral from the mineral class of oxides and hydroxides . It crystallizes in the monoclinic crystal system with the chemical composition Bi 2 O 3 and usually develops granular to massive mineral aggregates or earthy to powdery coatings in yellow, green-yellow or gray-green color. Crystals are seldom formed and then only microscopic.

It is very soft and easy to grind, opaque and shimmering or matt from yellow to gray to green. It consists of bismuth oxide Bi 2 O 3 with 89.7% bismuth and is contaminated with iron , copper and arsenic .

Etymology and history

Bismit was first described in 1753 by Johan Gottschalk Wallerius , who named the mineral after its composition. The type locality is Wolfgang Maaßen -Grubenfeld (Pucherschacht) near Neustädtel in the Ore Mountains .

classification

In the old (8th edition) and new systematics of minerals according to Strunz (9th edition) , the bismite belongs to the department of "oxides with the molar ratio metal: oxygen = 2: 3", this department in the new Strunz mineral classification The oxides with the molar ratio of metal: oxygen = 3: 5 and similar were expanded and more precisely divided according to the size of the cations . Accordingly, the mineral is now in the “With medium-sized cations” sub-section and forms a separate group there together with Sillénite and Sphaerobismoite .

The systematics of minerals according to Dana also assigns bismite to the class of oxides, but there in the division of "simple oxides with a cation charge of 3+ and the general formula A 2 O 3 ", where it forms a group with claudetite .

Modifications and varieties

The compound Bi 2 O 3 occurs dimorphically in nature and can crystallize in addition to bismite in the tetragonal structure of spherobismoite in space group P 4 2 2 1 2 (space group no. 94) . Template: room group / 94

Education and Locations

Bismite formed by oxidation of bismuth and, therefore, is usually found as a coating, rough and disseminated in pseudomorphs after Bismuthinit and aikinite .

So far, 156 sites have been registered (as of 2009), including some regions in Australia ; La Paz and Potosí departments in Bolivia; on the Rio Grande in Brazil; Guizhou , Qinghai and Yunnan in China; Baden-Württemberg (Black Forest), Bavaria (Bavarian and Upper Palatinate Forest), Hesse (Odenwald), North Rhine-Westphalia and Rhineland-Palatinate (Siegerland), Saxony-Anhalt (Harz), Saxony (Ore Mountains) and Thuringia (Vogtland) in Germany; Alsace , Auvergne and Brittany in France; Attica in Greece; England in Great Britain; Lombardy , Piedmont and Sardinia in Italy; Honshū and the Nansei Islands in Japan; Ontario in Canada; Kazakhstan ; Kivu in the Democratic Republic of the Congo; Antananarivo and Fianarantsoa in Madagascar; Durango in Mexico; Erongo and Kunene in Namibia; Aust-Agder in Norway; Carinthia and Styria in Austria; Lower Silesia in Poland; Russia (northern and western Siberian regions); Västmanland in Sweden; Canton of Valais in Switzerland; Banská Bystrica and near Košice in Slovakia; Bohemia in the Czech Republic; as well as many regions in the US .

Crystal structure of bismite

Crystal structure

Bismit crystallizes in the monoclinic crystal system in the space group P 2 1 / c (space group no. 14) with the lattice parameters a  = 5.8486  Å ; b  = 8.1661 Å, c  = 7.5097 Å and β = 113.00 ° as well as four formula units per unit cell . Template: room group / 14

See also

literature

Clifford Frondel : Mineralogy of the oxides and carbonates of bismuth In: American Mineralogist , Vol. 28, 1943, pp. 521-535 ( PDF )

Web links

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

Individual evidence

  1. a b c Webmineral - Bismite (English)
  2. a b c American Mineralogist Crystal Structure Database - Bismite (English, 1970)
  3. a b Bismite at mindat.org (English)
  4. a b Bismite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 66.9 kB )
  5. Mindat - Localities for Bismite