Lengenbachite

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Lengenbachite
Lengenbachite-ED.jpg
Lengenbachite needles on dolomite - size of the main crystal 1.5 mm
General and classification
chemical formula Pb 6 (Ag, Cu) 2 As 4 S 13
Mineral class
(and possibly department) 		Sulfides and sulfosalts - sulfosalts with SnS as a model
System no. to Strunz
and to Dana 		2.HF.30 ( 8th edition : II / E.15)
03.03.07.01
Crystallographic Data
Crystal system triclinic
Crystal class ; symbol triclinic pedial 1 or -pinacoidal 1
Room group (no.) P 1 or P 1 (No. 1 or 2)
Lattice parameters see crystal structure
Physical Properties
Mohs hardness 1.5 to 2
Density (g / cm 3 ) 5.80 to 5.85
Cleavage perfectly
colour steel gray with iridescent effects
Line color Brown black
transparency opaque
shine Metallic luster

Lengenbachite is a very rare mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the triclinic crystal system with the chemical composition Pb 6 (Ag, Cu) 2 As 4 S 13 and develops flat, thin, often corrugated sheets of up to 4 cm in size, steel-gray in color with iridescent effects.

Etymology and history

Lengenbachite was first found in 1904 in the "Lengenbach mine" in the Binn valley (canton Valais, Switzerland) and described by RH Solly, who named the mineral after its first location and type locality .

classification

In the now outdated system of minerals according to Strunz (8th edition) , lengenbachite is generally listed in the sulfosalts department. Since the revision of Strunz's mineral classification in the 9th edition , this section has also been more precisely subdivided according to the structural model and the chemical elements contained in the composition. The mineral is now located in the “H. Sulfosalts with SnS as a model "and there as the only one of his group in the subdivision" F. With SnS and PbS archetype structural units ”.

The systematics of minerals according to Dana assigns lengenbachite to the division of sulfosalts with the ratio 3 <z / y <4 and the (general) composition (A + ) i (A 2+ ) j [B y C z ] , where A = Metals, B = semi-metals, C = non-metals. He is the only one of his group to be found there in the unnamed group 3.3.7 .

Education and Locations

The mineral forms under hydrothermal conditions . It occurs together with the minerals pyrite , sphalerite and jordanite . So far, apart from the type locality in the Binn valley, no other sites are known.

Crystal structure

Lengenbachite crystallizes in a triclinic crystal system in space group P 1 or P 1 (space group no. 1 or 2). The crystal structure consists of two different subunits, one of which is pseudotetragonal with the lattice parameters a = 36.89  Å , b = 5.842 Å and c = 5.847 Å, α = 90.0 °, β = 92.0 ° and γ = 91 , 0 °. The second sub-cell is pseudo-hexagonal with the parameters a = 36.89 Å, b = 3.85 Å and c = 6.38 Å, α = 90.0 °, β = 90.0 ° and γ = 91.0 °.

See also

Individual evidence

  1. ↑ Grube Lengenbach - Brief description of the Lengenbachite ( Memento of the original from September 27, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.grube-lengenbach.ch

literature

Web links

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