Paravauxite
| Paravauxite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Fe 2+ Al 2 [OH | PO 4 ] 2 · 8H 2 O |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.DC.30 ( 8th edition : VII / D.10) 11.42.14.02 |
| Crystallographic Data | |
| Crystal system | triclinic |
| Crystal class ; symbol | triclinic pinacoidal; 1 |
| Space group | P 1 |
| Lattice parameters |
a = 5.23 Å ; b = 10.54 Å; c = 6.96 Å α = 106.9 °; β = 110.8 °; γ = 72.1 ° |
| Formula units | Z = 1 |
| Frequent crystal faces | {010}, {110}, {100}, { 1 10}, {1 2 0}, {011}, {001}, {0 1 1} and many others |
| Physical Properties | |
| Mohs hardness | 3 |
| Density (g / cm 3 ) | measured: 2.36; calculated: [2.37] |
| Cleavage | completely after {010} |
| Break ; Tenacity | mussely; brittle |
| colour | colorless, greenish white |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass luster, pearlescent luster on cleavage surfaces |
| Crystal optics | |
| Refractive indices |
n α = 1.552 to 1.554 n β = 1.558 to 1.559 n γ = 1.572 to 1.573 |
| Birefringence | δ = 0.020 |
| Axis angle | 2V = biaxial positive |
Paravauxite is a rarely occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the triclinic crystal system with the chemical composition Fe 2+ Al 2 [OH | PO 4 ] 2 · 8H 2 O and develops thick tabular to short prismatic crystals , but also parallel to radial mineral aggregates that are either colorless or greenish-white in color .
Etymology and history
The mineral was named because of its close relationship with vauxite.
Paravauxite was first discovered in 1922 in the "Siglo Veinte Mine" (Llallagua Mine) near Llallagua in Bolivia and described by Samuel George Gordon (1897–1953) who also described vauxite and metavauxite as other new minerals from this site .
classification
In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of paravauxite belonged to the mineral class of "phosphates, arsenates and vanadates" and then to the Department of "water containing phosphates with foreign anions " where he along with Ferrolaueit , Gordonit , Laueit , Mangangordonit , Sigloit and Ushkovit the "Paravauxite group" named after him with the system no. VII / D.10 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 paravauxite to the class of "phosphates, arsenates and vanadates" and there to the department of "phosphates, etc. with additional anions ; with H 2 O “. However, this section is further subdivided according to the size of the cations involved and the ratio of the additional anions to the cation complex RO 4 , so that the mineral is classified in the sub-section “With only medium-sized cations; (OH, etc.): RO 4 = 1: 1 and <2, "can be found, where it together with Ferrolaueit, Gordonit, 1 Maghrebit , Kastningit , Mangangordonit, Laueit, Pseudolaueit , Sigloit, Stewartit and Ushkovit the" Laueit group “With the system no. 8.DC.30 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns paravauxite to the class of "phosphates, arsenates and vanadates" and there to the category of "water-containing phosphates, etc., with hydroxyl or halogen". Here it is together with Vauxite , Sigloite, Gordonite, Mangangordonit, Kastningit and Maghrebit in the "Vauxite Group" with the system no. 42.11.14 within the subsection of " Water-containing phosphates etc., with hydroxyl or halogen with (AB) 4 (XO 4 ) 3 Z q × x (H 2 O) ".
Crystal structure
Paravauxite crystallizes triclinically in the space group P 1 (space group no. 2) with the lattice parameters a = 5.23 Å ; b = 10.54 Å; c = 6.96 Å; α = 106.9 °; β = 110.8 ° and γ = 72.1 ° as well as one formula unit per unit cell .
Modifications and varieties
The compound Fe 2+ Al 2 [OH | PO 4 ] 2 · 8 H 2 O is dimorphic , which means that it crystallizes as a monoclinic metavauxite in addition to the triclinic paravauxite.
Education and Locations
Paravauxite is formed in tin veins by hydrothermal processes . There it occurs in paragenesis with vauxite , metavauxite , wavellite , sigloite , crandallite , childrenite and quartz .
Apart from its type locality , the "Siglo Veinte Mine" (Llallagua Mine) near Llallagua in Bolivia, Paravauxite could also be found near Waidhaus (Bavaria) and Horscha (Saxony) in Germany; Sabugal in Portugal; as well as at Groton (New Hampshire) , Kings Mountain (North Carolina) and Bessemer City (North Carolina) (status: 2009).
See also
literature
- Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 648 (first edition: 1891).
Web links
- Mineral Atlas: Paravauxite (Wiki)
- RRUFF Database-of-Raman-spectroscopy - Paravauxite (English)
- American Mineralogist Crystal Structure Database - Paravauxite (English)
Individual evidence
- ↑ a b c d e Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 500 .
- ↑ Webmineral - Paravauxite (English)
- ↑ a b c d Paravauxite . 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 kB ]).
- ↑ a b c d e Mindat - Paravauxite (English)
- ↑ Samuel G. Gordon: Vauxite and Paravauxite, two new minerals from Llallagua, Bolivia . In: Proceedings of the Academy of Natural Sciences of Philadelphia . tape 75 , 1923, pp. 261-270 , JSTOR : 4063881 .
- ^ William Parrish: Memorial of Samuel George Gordon . In: American Mineralogist . tape 38 , no. 3-4 , 1953, pp. 301–308 ( minsocam.org [PDF; 542 kB ; accessed on May 10, 2018]).