Hocartite

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Hocartite
General and classification
other names

IMA 1967-046

chemical formula Ag 2 FeSnS 4
Mineral class
(and possibly department) 		Sulfides and sulfosalts
System no. to Strunz
and to Dana 		2.CB.15a ( 8th edition : II / C.06)
02.09.02.06
Crystallographic Data
Crystal system tetragonal
Crystal class ; symbol tetragonal-scalenohedral; 4 2 m
Room group (no.) I 4 2 m (No. 121)
Lattice parameters a  = 5.74  Å ; c  = 10.96 Å
Formula units Z  = 2
Twinning polysynthetic twins
Physical Properties
Mohs hardness 4th
Density (g / cm 3 ) calculated: 4.77
Cleavage Please complete!
colour brownish gray
Line color Please complete!
transparency opaque
shine Metallic luster

Hocartite is a rarely occurring mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the tetragonal crystal system with the composition Ag 2 FeSnS 4 , so from a chemical point of view it is a silver - iron - tin sulfide.

Hocartite is opaque and develops only small, irregular grains less than a millimeter in diameter, but can also be found in oriented intergrowth with stannite or enclosed in sphalerite and wurtzite . In incident light it is brownish-gray in color and has a metallic sheen .

With pirquitasite , Hocartite forms a seamless series of mixed crystals .

Etymology and history

Hocartite was first discovered in the “ Chocaya Mine” in the Municipio Atocha in the Bolivian Department of Potosí . It was described in 1968 by R. Caye, Y. Laurent, P. Picot, R. Pierrot and C. Lévy, who named the mineral after Raymond Hocart (1896-1983).

classification

In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the hocartite belonged to the mineral class of "sulfides and sulfosalts" and there to the department of "sulfides with the molar ratio metal: sulfur, selenium, tellurium = 1: 1", where he together with barquillite , briartite , černýite , famatinite , ferrokësterite , kësterite , kuramite , luzonite , permingeatite , petrukite , pirquitasite , rhodostannite , sakuraiite , stannite , toyohait and velikit form the "stannite group" with the system no. II / C.06 formed.

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also assigns hocartite to the class of "sulfides and sulfosalts" and there in the department of "metal sulfides, M: S = 1: 1 (and similar) ”. However, this section is further subdivided according to the predominant metals in the compound, so that the mineral can be found in the sub-section "with zinc (Zn), iron (Fe), copper (Cu), silver (Ag) etc." according to its composition is where, together with Černýit, Ferrokësterit, Idait , Kësterit, Kuramit, Pirquitasit, Stannit and Velikit, the "Stannit Group" with the system no. 2.CB.15a forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the hocartite to the class of "sulfides and sulfosalts" and there in the department of "sulfide minerals". Here he is together with Barquillit, Briartit, Černýit, Ferrokësterit, Kësterit, Kuramit, Pirquitasit, Sakuraiit, Stannit and Velikit in the "stannite group (tetragonal: I 4 2 m ) A 2 BCS type" with the system no. 02.09.02 within the subsection " Sulphides - including selenides and tellurides - with the composition A m B n X p , with (m + n): p = 1: 1 ".

Education and Locations

Hocartite is formed by hydrothermal processes at a relatively high temperature in deposits containing tin . As Begleitminerale occur among other Canfieldit , Franckeit , fluorite , cassiterite , Kylindrit , Pyrargyrite , siderite , dignified silver , sphalerite , Stannit , Suredait , tetrahedrite and wurtzite on.

As a rare mineral formation, Hocartite has only been found in a few sites so far, with around 30 sites being known (as of 2012). In addition to its type locality " Chocaya Mine", the mineral occurred in Bolivia in the mines "Ánimas", "Gran Chocaya" and "Siete Suyos", which are also located near Atocha, and in the " Colquiri Mine" in the La Paz department; the “San José Mine” near Oruro in the department of the same name and near Huaylla Vinto ( Porco ), Colquechaca (Aullagas), Tatasí and the “Colavi Mine” in the canton of Machacamarca in the Department of Potosí.

The only previously known site in Germany is the Bayerland mine near Pfaffenreuth in the Bavarian municipality of Leonberg and in Austria Hocartite has so far only been found on the Niedermüller Alp am Kreuzeck in the Kreuzeck group. Other locations include Argentina, China, France, Japan, Kyrgyzstan, Peru, Russia, Slovakia and the United States of America.

Crystal structure

Hocartite crystallizes tetragonally in the space group I 4 2 m (space group no. 121) with the lattice parameters a  = 5.74  Å and c  = 10.96 Å as well as 2 formula units per unit cell .

See also

literature

  • R. Caye, Y. Laurent, P. Picot, R. Pierrot, C. Lévy: La hocartite, Ag 2 SnFeS 4 , une nouvelle espèce minérale , in: Bulletin de la Société Française de Minéralogie et de Cristallographie , Volume 91 (1968 ), Pp. 383–387 ( PDF 416 kB , French with a brief description in English)

Web links

Individual evidence

  1. ↑ a b c d e Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  78 .
  2. ↑ Webmineral - Hocartite
  3. ↑ a b John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols: Hocartite , in: Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 61.1 kB )
  4. ^ Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp.  433 (first edition: 1891).
  5. ↑ Mindat - Number of localities for Hocartite
  6. ↑ Mindat - Hocartite