Franckeit

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Franckeit
Franckeite-228453.jpg
Franckeit from the San José mine , Oruro, Cercado Province, Oruro Department, Bolivia
General and classification
chemical formula Pb 21.7 Sn 9.3 Fe 4.0 Sb 8.1 S 56.9
Mineral class
(and possibly department) 		Sulphides and Sulphosalts - sulphides with a molar ratio of metal: sulfur, selenium, tellurium = 1: 1
System no. to Strunz
and to Dana 		2.HF.25b ( 8th edition : II / C.17)
01/03/04/02
Similar minerals Cylindrite
Crystallographic Data
Crystal system triclinic
Crystal class ; symbol triclinic pinacoidal; 1
Space group C 1 (No. 2, position 3)Template: room group / 2.3
Lattice parameters see crystal structure
Physical Properties
Mohs hardness 2.5 to 3
Density (g / cm 3 ) measured: 5.88 to 5.92; calculated: 5.88
Cleavage completely after {010}
colour grey black
Line color grey black
transparency opaque
shine Metallic luster

Franckeit is a rarely occurring mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the triclinic crystal system with the chemical composition Pb 21.7 Sn 9.3 Fe 4.0 Sb 8.1 S 56.9 and develops mostly rosette-like layered aggregates , but also thin, tabular or curved crystals in gray-black color.

Etymology and history

It got its name from the Francke brothers (Johann Heinrich Karl, 1832–1907 and Ernst Otto, 1838–1913), who worked as mining engineers and partners in the Chocaya mine in the municipality of Atocha (Bolivia) and brought it to Germany in 1877. In 1893 the mineral was first scientifically described by Prof. Alfred Stelzner in Freiberg .

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the Franckeit belonged to the mineral class of "sulfides and sulfosalts" and there to the department of "sulfides with the molar ratio of metal: S, Se, Te ≈ 1: 1", where together with Abramovite , Coirait , Herzenbergit , Kylindrit , Lévyclaudit , Mohit , Stistait , Suredait and Teallit, he created the "Herzenbergit series" with the system no. II / C.17 formed.

In contrast , the 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), classifies the Franckeit in the department of “sulfosalts with SnS as a model”. This is further subdivided according to the predominant metals in the compound or with compounds of special structure, so that the mineral can be found in the sub-section “With SnS and PbS archetype structural units” according to its composition and structure only together with Coirait forms the unnamed group 2.HF.25b .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Franckeit to the class of "sulfides" and there in the department of "sulfide minerals". Here it is together with Kylindrite, Incait , Potosíit , Abramovit and Coirait in the " Kylindrite group " with the system no. 03.01.04 within the subsection " Sulphosalts with the ratio z / y> 4 and the (general) composition (A + ) i (A 2+ ) j [B y C z ]", where A = metals, B = Semi-metals and C = non-metals.

Crystal structure

Franckeit crystallizes triclinic in space group C 1 (space group no. 2, position 3) in two defined sub-cells with the lattice parametersTemplate: room group / 2.3

  • pseudotetragonal: a  = 5.805 (8)  Å ; b  = 5.856 (16) Å; c  = 17.338 (5) Å; α = 94.97 (2) °; β = 88.45 (2) ° and γ = 89.94 (2) °
  • pseudohexagonal: a  = 3.665 (8)  Å ; b  = 6.2575 (16) Å; c  = 17.419 (5) Å; α = 95.25 (2) °; β = 95.45 (2) ° and γ = 89.97 (2) °

Modifications and varieties

Franckeit and Potosíit from the San José Mine, Oruro City, Cercado, Bolivia

Two varieties of Franckeits are known. The tin- rich Incaite was considered a separate mineral until 2007 and was first found in 1973 in Poopó in Bolivia . Potosíite , which is poor in tin , was first found in 1980 in Andacaba, also in Bolivia, and was considered an independent mineral until 1997.

Education and Locations

Franckeit formed hydrothermally especially in silver - and tin - deposits . It is accompanied by cassiterite , Kylindrite , wurtzite , zinkenite and others similar to Franckeit .

As a rare mineral formation, Franckeit could only be proven at a few sites, whereby so far (as of 2015) around 65 sites are known, most of them in Bolivia . In addition to its type locality Chocaya , the mineral was also found in the Potosí department in the Carguaicollo mine ( Antonio Quijarro province ), the Descubridora mine ( Chayanta province ), in the Andacaba deposit ( José María Linares province ), in the Cerro de Potosí , the Siglo XX mines ( Province of Rafael Bustillo ), Animas ( Municipio Atocha ), Asunta and Vetillas in the district of San Vicente , Santa Isabel ( Province of Sur Lípez ) and in the department of Cochabamba and the department of Oruro .

Other locations include Jujuy in Argentina , New South Wales in Australia , Guangxi in the People's Republic of China , Auvergne and Brittany in France , Western Thrace in Greece and California in the USA .

use

Franckeit has a tin content of about 13.68% and is extracted as tin ore when it is locally accumulated .

See also

literature

  • Alfred W. Stelzner: About Franckeit, a new ore from Bolivia. In: New Yearbook for Mineralogy. Volume 2 (1893), pp. 114–124 ( PDF 633.9 kB )
  • Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 36 .

Web links

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

Individual evidence

  1. ↑ a b c d E. Makovicky, V. Petříček, M. Dušek, D. Topa: The crystal structure of franckeite, Pb 21.7 Sn 9.3 Fe 4.0 Sb 8.1 S 56.9 . In: American Mineralogist. Volume 96 (2011), pp. 1686–1702 ( PDF 1.2 MB )
  2. ↑ a b Webmineral - Franckeite
  3. ↑ a b The numbering of this axis position does not correspond to the order of the International Tables for Crystallography , because it is not listed there.
  4. ↑ a b c Franckeite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 62 kB )
  5. ^ Alfred W. Stelzner: Ueber Franckeit, a new ore from Bolivia. In: New Yearbook for Mineralogy. Volume 2 (1893), pp. 114–124 ( PDF 633.9 kB )
  6. ↑ Mindat - Incaite
  7. ↑ Mindat - Potosíite
  8. ↑ Mindat - Number of localities for Franckeit
  9. ↑ Find location list for Franckeit at the Mineralienatlas and at Mindat