Cobalt neustädtelite
| Cobalt neustädtelite | |
|---|---|
| General and classification | |
| other names |
IMA 2000-012 |
| chemical formula | Bi 2 Fe 3+ Co 2+ O (OH) 3 (AsO 4 ) 2 |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.BK.10 ( 8th edition : VII / B.37) 04.41.09.03 |
| Crystallographic Data | |
| Crystal system | triclinic |
| Crystal class ; symbol | triclinic pinacoidal; 1 |
| Room group (no.) | P 1 (No. 2) |
| Lattice parameters |
a = 9.156 (1) Å ; b = 6.148 (1) Å; c = 9.338 (1) Å α = 83.24 (1) °; β = 70.56 (1) °; γ = 86.91 (1) ° |
| Formula units | Z = 1/2 |
| Physical Properties | |
| Mohs hardness | 4.5 |
| Density (g / cm 3 ) | calculated: 5.81 |
| Cleavage | good after {001} |
| Break ; Tenacity | clamshell; brittle |
| colour | brown, brown-red, black |
| Line color | light brown |
| transparency | transparent to translucent |
| shine | Diamond luster |
| Crystal optics | |
| Refractive indices |
n α = 2.020 n β = 2.090 n γ = 2.120 |
| Birefringence | δ = 0.100 |
| Optical character | biaxial negative |
| Axis angle | 2V = 65 (5) ° |
| Pleochroism | strong: X = brown, Y = yellow, Z = light yellow |
Cobalt neustädtelite is a very rarely occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the triclinic crystal system with the chemical composition Bi 2 Fe 3+ Co 2+ O (OH) 3 (AsO 4 ) 2 , so it is a bismuth - iron - cobalt arsenate with additional hydroxide ions .
Cobaltneustädtelite develops only small, tabular crystals with tabular habit up to about 0.2 millimeters in diameter of brown, brown-red or black color with a light brown streak color . The surfaces of the transparent to translucent crystal surfaces show a diamond-like sheen .
Etymology and history
Cobaltneustädtelite was first discovered together with Neustädtelite on the heaps of the "Güldener Falk" mine near Neustädtel (Schneeberg) in the Saxon Ore Mountains and described in 2002 by Werner Krause, Heinz-Jürgen Bernhardt, Catherine McCammon and Herta Effenberger, who named the mineral after its type of locality .
The type material of the mineral is kept in the collection of the State Museum for Mineralogy and Geology Dresden in Germany (catalog nos. 18328 and 18329).
classification
Already in the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the cobalt neustädtelite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "anhydrous phosphates, with foreign anions F, Cl, O, OH", where it formed the unnamed group VII / B.37 together with Brendelite , Neustädtelite , Medenbachite and Paulkellerite .
The 9th edition of Strunz's mineral systematics, which has been in force since 2001 and is used by the International Mineralogical Association (IMA), also assigns cobalt neustädtelite to the category of “phosphates etc. with additional anions; without H 2 O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of the additional anions (OH etc.) to the phosphate, arsenate or vanadate complex (RO 4 ), so that the mineral can be classified in the sub-section “With medium-sized and large cations; (OH etc.): RO 4 = 2: 1, 2.5: 1 “is to be found, where only together with Neustädtelite and Medenbachite the“ Medenbachite group ”with the system no. 8.BK.10 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns cobalt neustädtelite to the class of "phosphates, arsenates and vanadates" and there to the category of "anhydrous phosphates, etc., with hydroxyl or halogen". Here it is also together with Medenbachite and Neustädtelite in the " Medenbachite group " with the system no. 04/41/09 within the subsection “Anhydrous phosphates etc., with hydroxyl or halogen with (AB) 5 (XO 4 ) 2 Z q ”.
Education and Locations
The samples, which contain cobalt neustädtelite and neustädtelite, consist mainly of quartz , where the two minerals crystallize in small cavities. The accompanying minerals include goethite , limonite and prizingerite , and rarely also bismuthite , mixite and zeunerite .
As a rare mineral formation, Neustädtelite could only be detected at a few sites, whereby so far (as of 2013) fewer than 10 sites are known.
In addition to its type locality “Güldener Falk” mine, the mineral was also found on several mine dumps around Neustädtel and Schneeberg (Erzgebirge) such as the “Friedefürst”, “Junge Kalbe” and “Peter and Paul” mines (today Marx-Semler-Stolln ) found in Saxony.
The only other known site for cobalt neustädtelite so far is the "Espuela de San Miguel" pit near Villanueva de Córdoba near Córdoba in Spain (as of 2013).
Crystal structure
Cobaltneustädtelite crystallizes triclinically in the space group P 1 (space group no. 2) with the lattice parameters a = 9.156 (1) Å ; b = 6.148 (1) Å; c = 9.338 (1) Å; α = 83.24 (1) °; β = 70.56 (1) ° and γ = 86.91 (1) ° and ½ formula unit per unit cell .
See also
literature
- Werner Krause, Heinz-Jürgen Bernhardt, Catherine McCammon, Herta Effenberger: Neustädtelite and cobaltneustädtelite, the Fe 3+ - and Co 2+ -analogues of medenbachite. In: American Mineralogist. Volume 87 (2002), pp. 726-738 ( PDF 388.5 kB )
Web links
Individual evidence
- ↑ a b c d e f g h i Werner Krause, Heinz-Jürgen Bernhardt, Catherine McCammon, Herta Effenberger: Neustädtelite and cobaltneustädtelite, the Fe 3+ - and Co 2+ -analogues of medenbachite. In: American Mineralogist. Volume 87 (2002), pp. 726-738 ( PDF 388.5 kB )
- ↑ a b Mindat - Cobaltneustädtelite
- ↑ Mindat - Number of localities for Cobaltneustädtelite
- ↑ Find location list for cobalt neustädtelite at the Mineralienatlas and at Mindat