Rammelsbergite
| Rammelsbergite | |
|---|---|
 |
|
| General and classification | |
| other names |
White nickel gravel |
| chemical formula | NiAs 2 |
|
Mineral class (and possibly department) |
Sulfides and sulfosalts |
|
System no. to Strunz and to Dana |
2.EB.15a ( 8th edition : II / D.23) 02.12.02.12 |
| Similar minerals | Krutovite , pararammelsbergite |
| 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 = 4.76 Å ; b = 5.80 Å; c = 3.54 Å |
| Formula units | Z = 2 |
| Twinning | after {101} |
| Physical Properties | |
| Mohs hardness | 5.5 to 6 (VHN 100 = 30–758) |
| Density (g / cm 3 ) | measured: 7.1 (1); calculated: 7.091 |
| Cleavage | clearly after {101} |
| Break ; Tenacity | uneven; brittle |
| colour | tin white with a tinge of pink |
| Line color | grey black |
| transparency | opaque |
| shine | Metallic luster |
| Crystal optics | |
| Pleochroism | strong, yellow to pink, blue-white |
Rammelsbergite is a rarely occurring mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the orthorhombic crystal system with the chemical composition NiAs 2 , i.e. it contains nickel and arsenic in a ratio of 1: 2.
Rammelsbergite is opaque in every form and rarely forms well developed crystals with a tabular to short-prismatic habit . It is mostly found in the form of granular to massive, radial or fibrous mineral aggregates . Also known are crystal twins and pseudomorphoses based on, among other things, native silver .
Fresh mineral samples are pewter-white in color with a tinge of pink and have a strong metallic sheen . Over time, however, these start to run and become dark. Rammelsbergit leaves a gray-black line on the marking board .
Special properties
With a Mohs hardness of 5.5 to 6, rammelsbergite is one of the medium-hard minerals that, like the reference mineral orthoclase, can be scratched with a steel file. However, it reacts brittle to mechanical loads and breaks with an unevenly shaped fracture surface.
Etymology and history
Rammelsbergite has been known for a long time, the mineral was first described in 1845 by Wilhelm Ritter von Haidinger . The type locality is located near Schneeberg in the Ore Mountains . The mineral is named after the German mineralogist Karl Friedrich Rammelsberg .
The mineral is recognized by the International Mineralogical Association , but since the discovery took place before its founding in 1959, it is listed with the designation G for "Grandfathered".
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the Rammelsbergite belonged to the division of "Sulphides with the molar ratio of metal: S, Se, Te <1: 1", where it together with Costibit , Löllingit , Nisbit , Oenit , Safflorite and Seinäjokit the "Löllingite group" with the system no. II / D.23 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), classifies Rammelsbergite in the category of "Metal sulfides with 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 according to its composition in the subsection "M: S = 1: 2, with Fe, Co, Ni, PGE etc." , where together with Anduoite , Clinosafflorite , Löllingite, Nisbit, Omeiit and Safflorite, there is also 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 Rammelsbergite to the class of “sulfides and sulfosalts” and there to the “sulfide minerals” category. Here it is together with marcasite , ferroselite , Frohbergite , hastite , mattagamite , kullerudite , omeiite, anduoite, lollingite, Seinäjokit, safflorite and nisbit in the " marcasite group (Orthorhombian: 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".
Modifications and varieties
The compound NiAs 2 is dimorphic and occurs in nature in addition to the orthorhombic crystallizing rammelsbergite as cubic crystallizing krutovite and also orthorhombic, but in a different space group crystallizing pararammelsbergite .
Education and Locations
Rammelsbergite forms as a secondary mineral in hydrothermal veins at medium temperatures. Along with this, other nickel-cobalt minerals are also formed. Accordingly, the mineral is often Skutterudit socialized to find, but also with algodonite , Domeykit , Löllingit , Nickelin , safflorite and uraninite and dignified bismuth and silver encountered. Due to weathering, the mineral is occasionally coated with green annabergite .
As a rather rare mineral formation, Rammelsbergite can sometimes be abundant at various sites, but overall it is not very common. So far (as of 2013) around 200 sites are known.
In Germany , sites are found in the Erzgebirge , Harz , Black Forest and the Mansfeld region . Other European countries with Rammelsbergite finds are Austria (including near Lölling in Carinthia ), the Czech Republic , France , Greece , Italy , Spain and Great Britain .
Outside of Europe, rammelsbergite is found mainly in North America ( United States , Canada ).
Crystal structure
Rammelsbergite crystallizes orthorhombically with the space group Pnnm (space group no. 58) and the lattice parameters a = 4.76 Å ; b = 5.80 Å and c = 3.54 Å and 2 formula units per unit cell .
See also
literature
- W. Haidinger: Second class: Geogenide. XIII. Order. Kiese III. Cobalt gravel. Rammelsbergite . In: Handbook of Determining Mineralogy , Braumüller and Seidel, Vienna 1845, pp. 559–562 ( PDF 239.5 kB )
Web links
Individual evidence
- ↑ Webmineral - Rammelsbergite
- ^ 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 c d Rammelsbergite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 107.2 kB )
- ^ Helmut Schrätze, Karl-Ludwig Weiner: Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 266-267 .
- ^ Mindat - Rammelsbergite
- ↑ a b List of localities for Rammelsbergite in the Mineralienatlas and in Mindat