Stewartite
| Stewartite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Mn 2+ Fe 3+ 2 [OH | PO 4 ] 2 • 8 H 2 O |
|
Mineral class (and possibly department) |
Phosphates, arsenates, vanadates |
|
System no. to Strunz and to Dana |
8.DC.30 ( 8th edition : VII / D.09) 11/22/10/02 |
| Crystallographic Data | |
| Crystal system | triclinic |
| Crystal class ; symbol | triclinic-pinacoidal 1 |
| Space group | P 1 |
| Lattice parameters |
a = 10.398 Å ; b = 10.672 Å; c = 7.223 Å, α = 90.10 °; β = 109.10 °; γ = 71.83 ° |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 3 |
| Density (g / cm 3 ) | 2.94 |
| Cleavage | Please complete |
| colour | brownish yellow, orange yellow |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss, silk gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.612 to 1.630 n β = 1.653 to 1.658 n γ = 1.660 to 1.681 |
| Birefringence | δ = 0.048 to 0.051 |
| Optical character | biaxial negative |
| Pleochroism | clear: colorless - light yellow - yellow |
Stewartite is a rather seldom occurring mineral from the mineral class of phosphates , arsenates and vanadates. It crystallizes in the monoclinic crystal system with the chemical composition Mn 2+ Fe 3+ 2 [OH | PO 4 ] 2 • 8 H 2 O and develops tabular, leafy to needle-like crystals , but also radial, tufted aggregates of only a few millimeters in size in brownish-yellow or orange-yellow color.
Etymology and history
Stewartite was first discovered in 1912 in the "Stewart Mine" (in the Tourmaline Queen Mountains ) in the Pala District of San Diego County , California. Waldemar Theodore Schaller described this mineral together with hydroxyapatite and sicklerite in the "Journal of the Washington Academy of Sciences" (2, 143-145) and named it after its type locality .
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the stewartite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "water-containing phosphates with foreign anions ", where it belongs together with kastningite , metavauxite and pseudolaueit formed the unnamed group VII / D.09 .
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 stewartite 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: 1 “can be found where it is found together with ferrolaueit, gordonite, maghrebit ( IMA2005-044 ), kastningite , laueit , mangangordonite, paravauxite, pseudolaueit , sigloite and ushkovite 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 stewartite to the class of "phosphates, arsenates and vanadates" and there to the category of "water-containing phosphates, etc., with hydroxyl or halogen". Here he is together with Laueit, Pseudolaueit, Ushkovit and Ferrolaueit in the "Laueit Group" with the system no. 42.11.10 can be found within the subsection of " Water-containing phosphates etc., with hydroxyl or halogen with (AB) 4 (XO 4 ) 3 Z q × x (H 2 O) ".
Modifications and varieties
The compound Mn 2+ Fe 2 3+ [OH | PO 4 ] 2 · 8H 2 O is trimorphic and occurs in nature as triclinic stewartite as well as triclinic, but with different lattice parameters, and as monoclinic crystallizing pseudo-conductivity.
Education and Locations
Stewartit is a secondary mineral and formed by leaching primary phosphate deposits in granite - Pegmatiten .
Locations include Cordoba (San Alberto) in Argentina; Minas Gerais in Brazil; Limousin in France; Baden-Württemberg (district of Wolfach) and Bavaria (Bavarian and Upper Palatinate Forest) in Germany; Fianarantsoa in Madagascar; Erongo in Namibia; some regions in Portugal ; as well as several regions in the US .
Crystal structure
Stewartite crystallizes in the triclinic crystal system in the space group P 1 with the lattice parameters a = 10.398 Å , b = 10.672 Å, c = 7.223 Å, α = 90.10 °, β = 109.10 ° and γ = 71.83, as well as two Formula units per unit cell .
See also
Individual evidence
- ↑ a b c d Webmineral - Stewartite
- ↑ a b c Stewartite at mindat.org (engl.)
- ↑ Stefan Weiß: The large Lapis mineral directory . 5th edition. Christian Weise Verlag, Munich 2008, ISBN 3-921656-17-6 .
- ↑ Waldemar T. Schaller (1912): New manganese phosphates from the gem tourmaline field of Southern California , in: Journal of the Washington Academy of Sciences , Volume 2, pp. 143-145 ( PDF 223 kB )
- ↑ John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols: Laueite , in: Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 64.8 kB )
- ↑ Mindat - Localities for Stewartite
literature
- Paul Ramdohr , Hugo Strunz : Klockmann's textbook of mineralogy . 16th edition. Ferdinand Enke Verlag, 1978, ISBN 3-432-82986-8 , pp. 648 .
Web links
- Mineral Atlas: Stewartite (Wiki)
- John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols: Stewartite , in: Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 64.8 kB )