Namibit
| Namibit | |
|---|---|
 |
|
| General and classification | |
| other names |
IMA 1981-024 |
| chemical formula |
|
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.BB.50 ( 8th edition : VII / B.28) 05/38/08/01 |
| Crystallographic Data | |
| Crystal system | triclinic |
| Crystal class ; symbol | triclinic pinacoidal; 1 |
| Space group | P 1 (No. 2) |
| Lattice parameters |
a = 6.210 (1) Å ; b = 7.398 (1) Å; c = 7.471 (1) Å α = 90.10 (1) °; β = 108.73 (1) °; γ = 107.47 (1) ° |
| Formula units | Z = 2 |
| Frequent crystal faces | {101}, {111} |
| Twinning | after {011} pervasive and polysynthetic twins |
| Physical Properties | |
| Mohs hardness | 4.5 to 5 (VHN 100 and 200 = 473) |
| Density (g / cm 3 ) | measured: 6.86 (3); calculated: 6.91 |
| Cleavage | good after {001} |
| colour | dark green, olive green to greenish black |
| Line color | pistachio green |
| transparency | translucent |
| shine | not defined |
| Crystal optics | |
| Refractive indices | n α = 2.100 |
| Birefringence | δ = 2.100 |
| Optical character | biaxial negative |
| Pleochroism | weak: X = light yellowish green; Y = pistachio green; Z = dark green |
Namibite is a rarely occurring mineral from the mineral class of "phosphates, arsenates and vanadates". It crystallizes in the monoclinic crystal system with the chemical composition Cu (BiO) 2 [OH | VO 4 ] and is therefore a copper - bismuth oxide - vanadate with additional hydroxide ions .
Namibit mostly develops tabular or dendritic crystals and pseudomonoclinic twins , which are connected to radial to spherical mineral aggregates . The translucent crystals can be dark green, olive green or greenish black , depending on the foreign admixture, but the mineral always leaves a pistachio green streak on the marking board .
Etymology and history
Was first discovered in the cavities Namibit drusiger quartz - cores in the copper deposit near the community Khorixas (formerly welwitschia ) in the region Namibia Kunene . The mineral was described in 1981 by Oleg von Knorring (1915–1994) and Thure Georg Sahama , who named the mineral after the Namib desert , of which the find region largely consists.
The type material is kept at the University of Leeds in England and the University of Helsinki in Finland.
classification
Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the Namibite belonged to the mineral class of "phosphates, arsenates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 he together with Attakolith , Bertossait , Karminit , Leningradit , Paganoit , Palermoit and Sewardit the unnamed group VII / B.28 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), also assigns Namibit 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 according to its composition in the subsection “With exclusively medium-sized cations; (OH etc.): RO 4 ≤ 1: 1 “can be found where it is the only member of the unnamed group 8.BB.50 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Namibit to the class of "phosphates, arsenates and vanadates" and there in the department of "anhydrous phosphates etc.". Here it can be found together with Urusovite in the unnamed group 38.05.09 within the sub-section “Anhydrous phosphates etc., with various formulas”.
Crystal structure
Namibite crystallizes triclinically in the space group P 1 (space group no. 2) with the lattice parameters a = 6.210 (1) Å ; b = 7.398 (1) Å; c = 7.471 (1) Å; α = 90.10 (1) °; β = 108.73 (1) ° and γ = 107.47 (1) ° as well as two formula units per unit cell .
properties
The mineral is easily soluble in cold, dilute hydrochloric acid .
Education and Locations
Namibite is secondary to bismuth-containing , hydrothermal polymetallic deposits and granitic pegmatites . In addition to dignified bismuth and various bismuth minerals such as bismite , bismuthite , bismuthostibiconite and bismuth ferritite , Wittichenite , clinobisvanite , pucherite , beyerite , schumacherite , mixite , eulytite , chrysocolla can also occur as accompanying minerals .
As a rare mineral formation, Namibite could only be proven at a few localities, whereby so far (as of 2014) around 30 localities are known. In addition to its type locality Khorixas, more precisely the nearby pit "Mesopotamia 504", the mineral appeared in Namibia near Kandesei in the Kaokoveld .
In Germany, Namibit has so far been found in the Clara mine near Oberwolfach and the Hechtsberg quarry near Hausach in Baden-Württemberg, in the Pucherschacht of the Wolfgangmaßen mine field near Schneeberg in the Saxon Ore Mountains and the "Arme Hilfe" mine near Ullersreuth in Thuringia.
Other previously known sites are in Australia, Japan, Canada, Mexico, the Czech Republic, England in the United Kingdom (UK) and Arizona, Colorado, California and Nevada in the United States of America (USA).
See also
literature
- Oleg von Knorring , Thure Georg Sahama : Namibite, a new copper-bismuth-vanadium mineral from Namibia . In: Swiss mineralogical and petrographic messages . tape 61 , 1981, p. 7-12 .
Web links
- Mineral Atlas: Namibit (Wiki)
- Webmineral - Namibite
- Namibite search results. In: rruff.info. Database of Raman spectroscopy, X-ray diffraction and chemistry of minerals (RRUFF), accessed on May 3, 2019 .
- American-Mineralogist-Crystal-Structure-Database - Namibite. In: rruff.geo.arizona.edu. Retrieved May 3, 2019 .
Individual evidence
- ^ A b 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. 446 .
- ↑ a b c d Uwe Kolitsch , Gerald Giester: The crystal structure of namibite, Cu (BiO) 2 VO 4 (OH), and revision of its symmetry . In: American Mineralogist . tape 85 , 2000, pp. 1298–1301 (English, rruff.info [PDF; 1.5 MB ; accessed on May 3, 2019]).
- ↑ a b c d e f g Namibite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 69 kB ; accessed on May 3, 2019]).
- ↑ a b Namibite. In: mindat.org. Hudson Institute of Mineralogy, accessed May 3, 2019 .
- ^ Peter H. Nixon: Oleg von Knorring . In: Mineralogical Magazine . tape 58 , 1994, pp. 693–694 (English, [1] [PDF; 774 kB ; accessed on May 3, 2019]).
- ↑ a b Michael Fleischer , GY Chao, JA Mandarino : New mineral names . In: American Mineralogist . tape 67 , 1982, pp. 854–860 (English, [2] [PDF; 604 kB ; accessed on May 3, 2019]).
- ↑ Localities for Namibite. In: mindat.org. Hudson Institute of Mineralogy, accessed May 3, 2019 .
- ↑ Find location list for Namibit in the Mineralienatlas and Mindat