Tarbuttite
| Tarbuttite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Zn 2 [OH | PO 4 ] |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.BB.35 ( 8th edition : VII / B.06) 06/41/07/01 |
| Crystallographic Data | |
| Crystal system | triclinic |
| Crystal class ; symbol | triclinic pinacoidal; 1 |
| Room group (no.) | P 1 (No. 2) |
| Lattice parameters |
a = 5.50 Å ; b = 5.65 Å; c = 6.46 Å, α = 102.9 °; β = 102.8 °; γ = 86.8 ° |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 3.5 to 4 |
| Density (g / cm 3 ) | measured: 4.19; calculated: 4.21 |
| Cleavage | completely after {001} |
| Break ; Tenacity | uneven |
| colour | colorless, white, yellowish, reddish, greenish, brownish |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass luster, pearlescent luster on cleavage surfaces |
| Crystal optics | |
| Refractive indices |
n α = 1.660 n β = 1.705 n γ = 1.713 |
| Birefringence | δ = 0.053 |
| Optical character | biaxial negative |
| Axis angle | 2V = measured: 50 ° |
Tarbuttite is an occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the triclinic crystal system with the chemical composition Zn 2 [OH | PO 4 ], so it is a zinc phosphate with additional hydroxide ions .
Tarbuttite usually develops extensive, isometric to short prismatic or pseudocubic crystals up to about two centimeters in size, but also occurs in the form of sheaf-shaped mineral aggregates and crusty coatings. In its pure form, tarbuttite is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline training, it can also appear white and, due to foreign admixtures, assume a yellowish, reddish, greenish or brownish color, the transparency decreasing accordingly. Unharmed crystal surfaces have a glass-like sheen , whereas cleavage surfaces have a more mother-of-pearl shimmer .
Etymology and history
Tarbuttite was first discovered in the "Kabwe Mine" ( Broken Hill Mine ) near the city of the same name in Kabwe in the Central Province of Zambia and described in 1907 by Leonard James Spencer (1870-1959), who named the mineral after Percy Coventry Tarbutt. Tarbutt was director of the "Broken Hill Exploration Company" at the time and discovered the mineral near a cave with ice-age mammoth bones .
classification
In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the tarbuttite belonged to the mineral class of "phosphates, arsenates and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 Adamin , Eveit , Libethenit , Olivenit , Paradamin , Zincolibethenit and Zinkolivenit the "Libethenit-Gruppe" with the system no. VII / B.06 .
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 tarbuttite 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 "less than or equal" 1: 1 "can be found, where it is named after the" tarbuttite group "with the system no. 8.BB.35 and the other member Paradamin forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns tarbuttite to the class of "phosphates, arsenates and vanadates" and there to the category of "anhydrous phosphates, etc., with hydroxyl or halogen". Here he is together with Paradamit in the " Tarbuttitgruppe " with the system no. 41.06.07 within the subsection "Anhydrous phosphates etc., with hydroxyl or halogen with (A) 2 (XO 4 ) Z q ".
Education and Locations
Tarbuttite forms secondarily in the oxidation zone of zinc-bearing deposits . As accompanying minerals may include Cerussite , Descloizit , Hemimorphite , Hopeit and Parahopeit , Hydrozinkit , Pyromorphite , Scholzit , Smithsonite , Vanadinit and the limonite limonite occur.
As a very rare mineral formation, tarbuttite could so far (as of 2013) only be detected in a few samples from less than 10 sites. Its type locality "Kabwe Mine" is the only known site in Zambia to date.
Other previously known sites are Broken Hill and Reaphook Hill ( Flinderskette ) in Australia, Albères in the French Pyrénées-Orientales department , the "Scorpion Mine" near Rosh Pinah in Namibia and Iowa Gulch near Leadville in the US state of Colorado.
Crystal structure
Tarbuttite crystallizes triclinically in the space group P 1 (space group no. 2) with the lattice parameters a = 5.50 Å ; b = 5.65 Å; c = 6.46 Å; α = 102.9 °; β = 102.8 ° and γ = 86.8 ° as well as 2 formula units per unit cell .
The crystal structure consists of chains of edge-sharing ZnO 3 (OH) 2 assemblies that form parallel trigonal dipyramids [010] and dimers of two edge-sharing ZnO 3 (OH) trigonal dipyramids. Both modules and RO 4 - tetrahedra are connected with each other via the corners and form a 3-dimensional scaffold.
See also
literature
- LJ Spencer: Societies and Academies: Mineralogical Society. In: Nature. Volume 76, 1907, pp. 215-215 ( rruff.info PDF; 144 kB).
- LJ Spencer: On hopeite and other zinc phosphates and associated minerals from Broken Hill mines, North-Western Rhodesia. In: Mineralogical Magazine. Volume 15, 1908, pp. 1–38 ( rruff.info PDF; 1.7 MB).
- Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 629 (first edition: 1891).
- Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p. 645 .
Web links
- Mineral Atlas: Tarbuttite (Wiki)
- Database-of-Raman-spectroscopy - Tarbuttite.
- American-Mineralogist-Crystal-Structure-Database - Tarbuttite.
Individual evidence
- ↑ a b c d e 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. 444 .
- ↑ Webmineral - Tarbuttite.
- ↑ a b c Tarbuttite. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America. 2001 ( handbookofmineralogy.org PDF; 65.2 kB).
- ↑ a b c Mindat - Tarbuttite.
- ↑ Mindat - Number of localities for Tarbuttite.
- ↑ Find spot list for tarbuttite at the Mineralienatlas and at Mindat .