Stillwaterit
| Stillwaterit | |
|---|---|
| General and classification | |
| other names |
IMA 1974-029 |
| chemical formula | Pd 8 As 3 |
|
Mineral class (and possibly department) |
Sulfides and sulfosalts |
|
System no. to Strunz and to Dana |
2.AC.10 ( 8th edition : II / A.05) 02.16.04.01 |
| Crystallographic Data | |
| Crystal system | hexagonal |
| Crystal class ; symbol | 3 or 3 |
| Space group | P 3 or P 3 |
| Lattice parameters | a = 7.392 to 7.399 Å ; c = 10.311 Å Please complete the source as an individual reference |
| Formula units | Z = 3 Please complete the source as an individual reference |
| Twinning | very rarely in sanded areas |
| Physical Properties | |
| Mohs hardness | 4.5 |
| Density (g / cm 3 ) | 10.96 |
| Cleavage | Please complete |
| colour | creamy gray |
| Line color | Please complete |
| transparency | opaque |
| shine | metallic |
Stillwaterite is a very rarely occurring mineral from the mineral class of sulfides and sulfosalts . It crystallizes in the hexagonal crystal system with the chemical composition Pd 8 As 3 and forms anhedral grains of up to 265 μm in size and a creamy gray color.
Etymology and history
The mineral was discovered in 1975 by LJ Cabri, JLG Laflamme, JM Stewart, JF Rowland and Tzong R. Chenin in its type locality , the Stillwater Complex , a rock formation in the US state of Montana . It is named after this too.
classification
In the Strunz system , Stillwaterite is one of the alloys and alloy-like compounds, a subgroup of sulfides and sulfosalts. After the 8th edition , it forms together with Arsenopalladinit , Atheneit , Genkinit , Itoigawait , Majakit , Menshikovit , Mertieit-I , Mertieit-II , Palladoarsenid , Palladobismutoarsenid , Palladodymit , Polkanovit , Rhodarsenid , stibiopalladinite , Ungavait and Vincentit a group. In the 9th edition it forms with arsenopalladinite, mertieite-II and palarstanide a subgroup of the compounds of semimetals with platinum group elements (PGE).
In the systematics according to Dana , which is mainly used in the English-speaking world , it forms a separate subgroup of sulfides, selenides and tellurides with different formulas.
Education and Locations
Stillwaterite forms in layered, ultramafic igneous rocks . It is associated with gold , pallado arsenide , sperrylite , braggite , hollingworthite , chalcopyrite , diginite , pentlandite and pyrrhotite .
Only a few locations are known of the very rare mineral. In addition to its type locality, Stillwaterit was found in Lapland ( Finland ), Porsanger in Norway , the Russian Oblast Murmansk , and in the Bushveld complex in South Africa .
Crystal structure
Stillwaterite crystallizes in the hexagonal crystal system in the space group P 3 or P3 with the lattice parameters a = 7.392–7.399 Å and c = 10.311 Å as well as three formula units per unit cell .
See also
Individual evidence
literature
- Stillwaterit in: Anthony et al .: Handbook of Mineralogy , 1990, 1, 101 ( pdf ).