Laforêtit
| Laforêtit | |
|---|---|
| General and classification | |
| other names |
IMA 1995-006 |
| chemical formula | AgInS 2 |
|
Mineral class (and possibly department) |
Sulfides and sulfosalts |
|
System no. to Strunz and to Dana |
2.CB.10 ( 8th edition : II / C.03) 02.09.01.06 |
| Crystallographic Data | |
| Crystal system | tetragonal |
| Crystal class ; symbol | 4 2 m |
| Space group | I 4 2 d |
| Lattice parameters | a = 5.88 Å ; c = 11.21 Å Please complete the source as an individual reference |
| Formula units | Z = 4 Please complete the source as an individual reference |
| Twinning | polysynthetic - lamellar |
| Physical Properties | |
| Mohs hardness | 3 to 3.5 |
| Density (g / cm 3 ) | 4.93 |
| Cleavage | Please complete |
| colour | Gray |
| Line color | grey black |
| transparency | opaque |
| shine | Please complete |
Laforêtite is a very rare mineral from the mineral class of sulfides and sulfosalts . It crystallizes in the tetragonal crystal system with the chemical composition AgInS 2 and forms inclusions up to 30 µm in galena .
Etymology and history
The mineral was first discovered in 1999 by N. Meisser, P. Thelin, P.-J. Chiappero and C. Maurel found in the Montgros mine near Pinols in the Haute-Loire department ( France ). They named it after the French metallurgist Claude P. Laforêt.
classification
In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the laforêtite belonged to the mineral class of "sulfides and sulfosalts" and there to the department of "metal (M): sulfur (S), selenium, tellurium = 1: 1" , where together with chalcopyrite , eskebornite , gallite , lenaite and roquesite it formed an independent group.
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 laforêtite to the class of "sulfides and sulfosalts" and there into the department of "metal sulfides with the molar ratio 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 chalcopyrite, eskebornite, gallite, haycockite , lenaite, mooihoekite , putoranite , roquesite and talnakhite, the "chalcopyrite group" with the system no. 2.CB.10 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the laforêtite to the class of "sulfides and sulfosalts" and there in the department of "sulfide minerals". Here it is together with chalcopyrite, eskebornite, gallite, roquesite and lenaite in the "chalcopyrite group (tetragonal: I 4 2 d )" with the system no. 02.09.01 to be found within the subsection of " Sulphides - including selenides and tellurides - with the composition A m B n X p , with (m + n): p = 1: 1 ".
Education and Locations
Laforêtite forms under hydrothermal conditions. Depending on where it was found, it is associated with galena , sphalerite , barite , anchorite and quartz or sphalerite, hocartite and pyrargyrite .
In addition to the Tsumeb mine, finds are only known from the Toyoha mine near Sapporo in Japan .
Crystal structure
Laforêtite crystallizes in the tetragonal crystal system in the space group I 4 2 d with the lattice parameters a = 5.88 Å and c = 11.21 Å as well as four formula units per unit cell .
See also
Individual evidence
literature
- Laforêtit in: Anthony et al .: Handbook of Mineralogy , 1990, 1, 101 ( pdf )