Diadochit
| Diadochit | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Fe 3+ 2 [OH | SO 4 | PO 4 ] • 6H 2 O |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.DB.05 ( 8th edition : VII / D.05) 43.05.02.01 |
| Crystallographic Data | |
| Crystal system | triclinic |
| Crystal class ; symbol | triclinic pinacoidal; 1 |
| Space group | P 1 (No. 2) |
| Lattice parameters |
a = 9.57 Å ; b = 9.72 Å; c = 7.31 Å α = 98.7 °; β = 107.9 °; γ = 63.9 ° |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 3 to 4 |
| Density (g / cm 3 ) | measured: 2.0 to 2.4; calculated: [2.32] |
| Cleavage | no |
| Break ; Tenacity | Shelly to uneven, brittle and brittle |
| colour | yellowish brown, greenish yellow, reddish brown |
| Line color | pale yellow to brownish yellow |
| transparency | translucent to opaque |
| shine | Glass gloss, earthy matt |
| Crystal optics | |
| Refractive indices |
n α = 1.615 n β = 1.618 to 1.638 n γ = 1.665 to 1.670 |
| Birefringence | δ = 0.050 to 0.055 |
| Optical character | biaxial positive |
Diadochite is a rather seldom occurring mineral from the mineral class of sulfates with the chemical composition Fe 3+ 2 [OH | SO 4 | PO 4 ] · 6H 2 O.
Diadochite crystallizes in the triclinic crystal system , but develops mainly bulbous, massive mineral aggregates or crusty coatings, rarely also microscopic, six-sided, flat crystals of yellow-brown, red-brown or yellow-green color.
Etymology and history
Diadochite was first described in 1837 by August Breithaupt , who named the mineral after the ancient Greek word διάδοχος for successor , as it was exchanged as a secondary mineral to pitticit (Fe 3+ 2 (AsO 4 ) (SO 4 ) (OH) · nH 2 O) followed by arsenic by phosphorus . The type locality is Arnsbach , a district of Probstzella in Thuringia.
classification
In the old (8th edition) and new systematics of minerals (9th edition) according to Strunz , the diadochite belongs to the division of "water-containing phosphates with foreign anions ". Since the new Strunz'schen mineral classification, this department is more precisely divided according to the size of the cations involved and the ratio of the hydroxyl group to the cation complex. The mineral can be found accordingly in the subsection “With only medium-sized cations; (OH etc.): RO 4 <1: 1 “.
The systematics of minerals according to Dana classifies the diadochite in the section " Compound phosphates etc., (hydrated compound anions with hydroxyl or halogen) ".
Crystal structure
Diadochite crystallizes triclinically in the space group P 1 (space group no. 2) with the lattice parameters a = 9.57 Å ; b = 9.72 Å; c = 7.31 Å; α = 98.7 °; β = 107.9 ° and γ = 63.9 ° as well as two formula units per unit cell .
Varieties and modifications
A water-resistant, finely crystalline substance with a similar composition (~ 20% P 2 O 5 , ~ 27% SO 4 ) is sometimes referred to as Destinezite , and sometimes viewed as a crystalline variety of Diadochite. It coats the rock with light beige to gray-brown crusts, even in dry, airy places. The Saalfeld fairy grottoes (Thuringia) are considered to be the type locality .
Education and Locations
Diadochite is formed as a secondary mineral during the partly microbacterially induced oxidation of iron disulphide ( marcasite , pyrite ) and phosphorite to sulfuric and phosphoric acid, which then dissolve iron and other metals from the surrounding rocks (replacement of weak acids by strong ones). In former alum - mines it often occurs en masse, where it forms part colorful stalactites , flowstone and coating. Accompanying minerals include delvauxite , pitticit , vashegyite , vivianite , wavellite and other phosphate minerals.
Diadochite has so far been found at more than 70 sites (as of 2009), including at Lubango in Angola; near Mons , Visé and Anhée in Belgium; Baden-Württemberg , Bavaria , North Rhine-Westphalia , Saxony and Thuringia in Germany; at Huelgoat and Peycheguard in France; England in Great Britain; Italy ; in the Canadian Yukon ; in the Gurktal Alps and near Leoben in Austria; Romania ; Slovakia ; in Czech Bohemia ; Hungary ; as well as in several regions of the USA .
See also
literature
- Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 181 .
- Paul Ramdohr , Hugo Strunz : Klockmann's textbook of mineralogy . 16th edition. Ferdinand Enke Verlag, 1978, ISBN 3-432-82986-8 , pp. 649 .
- Bernd Ullrich, Kay-Uwe Hantsch, Klaus Müller, Heiner Siedel: Secondary mineral formations from the alum slate mine “Morassina” near Schmiedefeld on Rennweg (Saalfelder Höhe) in the Thuringian Slate Mountains . In: Contributions to the geology of Thuringia . 2005, p. 41–69 ( PDF 3.3 MB ( Memento from January 4, 2016 in the Internet Archive )).
Web links
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. 495 .
- ↑ Webmineral - Diadochite (English)
- ↑ a b c Diadochite . 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; 66 kB ; accessed on May 3, 2018]).
- ↑ a b c d Mindat - Diadochite (English)
- ↑ Mindat - Localities for Diadochite (English).