Omeiit
| Omeiit | |
|---|---|
| General and classification | |
| chemical formula | OsAs 2 |
|
Mineral class (and possibly department) |
Sulfides and sulfosalts |
|
System no. to Strunz and to Dana |
2.EB.15a ( 8th edition : II / D.20) 02.12.02.07 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 / m 2 / m 2 / m |
| Room group (no.) | Pnnm (No. 58) |
| Lattice parameters | a = 5.41 Å ; b = 6.17 Å; c = 3.02 Å |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 7th |
| Density (g / cm 3 ) | calculated: 11.2 |
| Cleavage | parallel to the longitudinal axis |
| Break ; Tenacity | brittle |
| colour | steel gray |
| Line color | Please complete |
| transparency | opaque |
| shine | metallic |
| Other properties | |
| Chemical behavior | insoluble in HCl and HNO 3 |
Omeiite is a very rarely occurring mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the orthorhombic crystal system with the composition OSAS 2 , so it is chemically seen a osmium - arsenide . Since omeiite forms a mixed crystal row with anduoite (RuAs 2 ) and is therefore usually found in nature with a small proportion of ruthenium , the mixed crystal formula is also given accordingly with (Os, Ru) As 2 .
Omeiit only develops microscopic, tabular to prismatic crystals of steel-gray color with a metallic sheen . When polished, however, Omeiit appears white with a tinge of yellow in the air and a more milky yellow in oil.
Special properties
Omeiite is clearly optically anisotropic and has a weak pleochroism from yellow to grayish yellow. The mineral is insoluble in hydrochloric acid and nitric acid .
Etymology and history
Was first discovered Omeiit ( Chinese 峨眉矿 , Pinyin Emeikuang ) in the copper-nickel- PGE - deposit "Yangliuping" in a circle Rongzhag ( Danba ) in the Chinese province of Sichuan . It was described in 1978 by Ren Yingxin, Hu Qinde and Xu Jinga, who named the mineral after the mountain Emei Shan ( O-mei Shan ), which is known in the region .
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the omeiite belonged to the department of "Sulphides with the molar ratio of metal: S, Se, Te <1: 1", where it together with anduoite , ferroselite , Frohbergite , iridarsenite , Kullerudit , Marcasit and Mattagamit the "Marcasitgruppe" with the system no. II / D.20 formed.
The 9th edition of Strunz's mineral systematics, which has been in force since 2001 and is used by the International Mineralogical Association (IMA), classifies the omeiite in the category of “metal sulfides with a molar ratio of M: S ≤ 1: 2”. However, this is further subdivided according to the exact molar ratio and the predominant metals in the compound, so that the mineral can be found in the sub-section "M: S = 1: 2, with Fe, Co, Ni, PGE etc." according to its composition , where together with Anduoite, Klinosafflorite , Löllingite , Nisbit , Rammelsbergite and Safflorite the "Löllingite group" with the system no. 2.EB.15a forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the omeiite to the class of "sulfides and sulfosalts" and there in the department of "sulfide minerals". Here it is in the " marcasite group (Orthorhombic: Pnnm) " with the system no. 02.12.02 within the subsection "Sulphides - including selenides and tellurides - with the composition A m B n X p , with (m + n): p = 1: 2".
Education and Locations
Omeiite forms in transformed ultramafic intrusions . As Begleitminerale occur among other bornite , chalcopyrite , Cubanit , galena , gold and silver-containing gold, Kotulskit , linneite , magnetite , Michenerit , pentlandite , Sperrylith , sphalerite , Sudburyit , Testibiopalladit , pyrrhotite and Violarite on.
As a very rare mineral formation, omeiite could only be detected in a few samples from less than 10 sites. Its type locality "Yangliuping" in Sichuan is the only known site in China so far.
Other previously known sites are the "O'Toole" deposit near Fortaleza de Minas in the Brazilian state of Minas Gerais , Pefki in the Pindos Mountains in the Greek region of Epirus , the chrome deposit "Kapitanov" near Zvenyhorodka in the Ukrainian Oblast of Cherkassy and West Nottingham Township in Chester County, Pennsylvania in the United States.
Crystal structure
Omeiite crystallizes orthorhombically in the space group Pnnm (space group no. 58) with the lattice parameters a = 5.41 Å , b = 6.17 Å and c = 3.02 Å, as well as two formula units per unit cell .
See also
literature
- Ren Yingxin, Hu Qinde, and Xu Jingao (1978): "A Preliminary Examination of the New Platinum Group Material - Omeiit OsAs2". Dizhi xuebao (Acta Geologica Sinica)] 52 (2), pp. 163-167 (Chinese with English abstract).
- Michael Fleischer, George Y. Chao and Adolf Pabst: New Mineral Names. In: American Mineralogist , Volume 64 (1979), p. 464, 1979 ( PDF 444 kB )
Web links
Individual evidence
- ↑ a b c IMA / CNMNC List of Mineral Names February 2013 (PDF 1.3 MB)
- ↑ Webmineral - Omeiite
- ^ A b c 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. 108 .
- ↑ a b Mindat - Omeiite
- ↑ Omeiite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 59.8 kB )