Picotpaulite

from Wikipedia, the free encyclopedia
Picotpaulite
General and classification
chemical formula TlFe 2 S 3
Mineral class
(and possibly department) 		Sulfides and sulfosalts
System no. to Strunz
and to Dana 		2.CB.60 ( 8th edition : II / C.05)
02.09.09.02
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol mmC
Space group C mcm
Lattice parameters a  = 9.083 (6)  Å ; b  = 10.754 (6) Å; c  = 5.412 (4) Å
Formula units Z  = 4
Twinning Penetration Twins Along {120}
Physical Properties
Mohs hardness 2
Density (g / cm 3 ) 5.2
Cleavage Please complete!
colour bronze
Line color Please complete!
transparency opaque
shine metallic

Picotpaulite is a very rare mineral from the mineral class of sulfides and sulfosalts . It crystallizes in the orthorhombic crystal system with the chemical composition Tl 2 FeS 3 and forms pseudo-hexagonal bronze-colored plates up to two millimeters in size.

Etymology and history

The mineral was first found in 1970 by Zdenek Johan, Roland Pierrot, Henry-Jean Schubnel and Francois Permigneate in Allchar , Macedonia. They named it after the French mineralogist Paul Picot.

classification

In the Strunz system , picotpaulite is counted among the metal sulfides with a ratio of metal to sulfur, selenium or tellurium of 1: 1. After the 8th edition , it forms a group with Raguinit . In the 9th edition , it also forms a subgroup of sulfides with zinc , iron , copper or silver with raguinite .

In the Dana systematics, together with sternbergite , it forms a subgroup of sulphides, selenides and tellurides with the composition A m B n X p , with (m + n): p = 1: 1.

Education and Locations

Picotpaulite forms under hydrothermal conditions together with other thallium and arsenic minerals. It is associated with realgar , lorandite , raguinite and pyrite .

Only a few sites are known of the very rare mineral. In addition to the type locality , picotpaulite was only found in Nanhua in the Chinese province of Yunnan .

Crystal structure

Picotpaulite crystallizes in the orthorhombic crystal system in the space group C mcm with the lattice parameters a = 9.083 (6)  Å , b = 10.754 (6) Å and c = 5.412 (4) Å as well as four formula units per unit cell .

The structure of picotpaulite belongs to the CsCu2Cl3 structure type and picotpaulite is isotypic with rasvumite (KFe 2 S 3 ) and pautovite (CsFe 2 S 3 ).

The iron ions are tetrahedrally surrounded by four sulfur anions. These FeS 4 tetrahedra are linked via corners (common S anions) to form double chains that extend along the c-axis. The Fe-Fe distances along these double chains are quite small at around 2.7 Å, which suggests strong interactions (Fe 2+ -Fe 3+ - electron exchange ). The mean charge of the Fe ions is given as +2.5.

The singly charged talium ions (Tl - ) are surrounded by 10 S ions in the form of a square antiprism with an adjacent trigonal prism. These TlS 10 polyhedra form zigzag chains in the direction of the c-axis and link the FeS 4 double chains with one another.

See also

Individual evidence

  1. ↑ a b c d Balić-Žunić, Tonči; Karanović, Ljiljana; Poleti, Dejant: Crystal Structure of Picotpaulite, TlFe 2 S 3 , from Allchar, FYR Macedonia In: Acta Chimica Slovenica ; 2008, 55, p. 801 ( abstract )
  2. ^ Zdenek Johan, Roland Pierrot, Henry-Jean Schubnel and Francois Permigneat: La Picotpaulite, TlFe 2 S 3 , une nouvelle espèce minerale. In: Bull. Soc. Franc. Mineral., Cristallogr. 1970, 93, pp. 545-549 ( abstract in American Mineralogist ; PDF; 438 kB).
  3. ^ New Dana Classification of Sulfide Minerals

literature

  • Picotpaulite in: Anthony et al .: Handbook of Mineralogy , 1990, 1, 101 ( pdf ).

Web links