Cadmoselite

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Cadmoselite
General and classification
chemical formula CdSe
Mineral class
(and possibly department) 		Sulfides and sulfosalts
System no. to Strunz
and to Dana 		2.CB.45 ( 8th edition : II / C.13)
08/02/07/03
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol dihexagonal-pyramidal 6 mm
Space group P 6 3 mc
Lattice parameters a  = 4.30  Å ; c  = 7.02 Å
Formula units Z  = 2
Physical Properties
Mohs hardness 4th
Density (g / cm 3 ) measured: 5.47; calculated: 5.807
Cleavage perfectly
Break ; Tenacity brittle
colour black; light gray in incident light; pale brown in oil with internal, brownish reflections
Line color black
transparency translucent to opaque
shine Diamond luster, resin luster

Cadmoselite is a very rarely occurring mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the hexagonal crystal system with the composition CdSe, so from a chemical point of view it is cadmium selenide .

Cadmoselite only develops very small, hexagonal pyramidal crystals in the range of a few tenths of a millimeter with horizontal stripes . The color of the mineral is unusually changeable. It looks black in indirect lighting, but light gray in incident light. When dipped in oil, the color appears pale brown with inner, brownish reflections.

Etymology and history

Cadmoselite was first found in 1957 in the “Ust'Uyok” deposit near Turan (South Siberia, Russia) and described by EZ Buryanova, GA Kovalev and AI Komkov, who named the mineral cadmium and selenium after its composition .

classification

In the old (8th edition) and the new systematics of minerals according to Strunz (9th edition) , the cadmoselite belongs to the division of "sulfides and sulfosalts with a molar ratio of metal: sulfur, selenium, tellurium = 1: 1". However, the 9th edition of Strunz's mineral classification now subdivides more precisely according to the type of cations involved and the mineral is accordingly in the sub-section "with zinc (Zn), iron (Fe), copper (Cu), silver (Ag) , etc. ”, where it forms its own group together with hypercinnabarite , greenockite , rambergite and wurtzite .

The systematics used in the English-speaking world of minerals according to Dana assigns the cadmoselite to the subdivision of "Sulphides including selenides and tellurides with the general composition A m B n X p and the molar ratio (m + n): p = 1: 1". There it is found together with greenockite, rambergite and wurtzite in the wurtzite group (hexagonal: P63mc) .

Education and Locations

Cadmoselite forms in sedimentary layers under reducing conditions with medium to high alkalinity. Accompanying minerals include calcite , clausthalite , ferroselite , greenockite , laumontite , pyrite and genuine selenium .

Except at its type locality "Ust'Uyok" in Russia could cadmoselite so far only in the "Kidd Creek Mine" in the district of Cochrane (Ontario) in Canada and in the "Tumiñico Mine" Sierra de Cacho in the Argentine province of La Rioja found (Status: 2009).

Crystal structure

Cadmoselite crystallizes hexagonally in the space group P 6 3 mc with the lattice parameters a  = 4.30  Å and c  = 7.02 Å and two formula units per unit cell .

See also

Individual evidence

  1. ↑ a b c Webmineral - Cadmoselite (English)
  2. ↑ a b American Mineralogist Crystal Structure Database - Cadmoselite (English, 1963, 1993)
  3. ↑ a b Handbook of Minerals - Cadmoselite (English, PDF 56.6 kB)
  4. ↑ Mindat - Cadmoselite (English)
  5. ↑ American Mineralogist Crystal Structure Database - Cadmoselite (English, 1963, 1993)

literature

Web links