Diadochite
Diadochite is a rarely occurring mineral from the mineral class of sulfates. It crystallizes in the triclinic crystal system with the chemical composition Fe3 2 ( PO4 ) (SO4 ) (OH) · 6H2O, but it is predominantly amorphous, nodular, massive mineral aggregates or crusty coatings, rarely microscopically small, six- sided, flat crystals of yellow-brown reddish-brown or yellow-green color,
Etymology and history
Diadochite 1837 was first described by August Breithaupt, of the mineral from the ancient Greek word διάδοχος for successor named because it as a secondary mineral which Pitticit ( Fe3 2 ( AsO4 ) (SO4 ) (OH) • n H2O) by replacement of arsenic by phosphorus followeth. As a type locality applies Arnsbach ( Hockeroda ) in Saalfeld / Saale in Thuringia.
Classification
In the old ( 8th edition ) and new classification of minerals ( 9th Edition ) by Strunz heard the Diadochite to the Department of " water -containing phosphates with foreign anions ." Since the new Strunz'schen Mineral classification, this department is, however, precisely also on the size of the involved cations and the ratio of hydroxyl group divided into cation complex. The mineral is found in accordance with the subdivision "With only medium-sized cations, (OH, etc.): RO 4 < 1:1".
The classification of minerals according to Dana assigns the Diadochite in the department " Composite phosphates, etc., ( Hydrated composite anions with hydroxyl or halogen) " a.
Varieties and modifications
A water-resistant, fine crystalline substance with similar composition (~ 20 % P2O5 27% ~ SO4 ) is called partly as Destinezit considered partly as a crystalline variety of Diadochits. With light beige to gray- brown crusts she pulls the rock also in dry, airy places. As the type locality Saalfeld Fairy Grottoes ( Thuringia).
Education and Locations
Diadochite forms as a secondary mineral in the part microbacterially induced oxidation of iron disulfide ( marcasite, pyrite ) and phosphorite to sulfuric and phosphoric acid, which then iron and other metals from the surrounding rocks dissolve ( suppression of weak acids by strong ). In former alum mines he often occurs en masse, and here forms part of colorful stalactites, flowstone and coatings. Accompanying minerals include Delvauxite, Pitticit, Vashegyit, vivianite, Wavellite and other phosphate minerals.
Diadochite could be proven so far to more than 70 localities (as of 2009), so among other things at Lubango in Angola; at 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 the United Kingdom; Italy; in the Yukon; Gurktal Alps and in Leoben in Austria; Romania; Slovakia; Bohemia in the Czech Republic; Hungary; as well as in several regions of the United States.
Crystal structure
Diadochite crystallizes in the triclinic space group P1 ( Raumgruppen-Nr. 2) with the lattice parameters a = 9.566 Å; b = 9.730 Å; c = 7.331 Å; α = 98.67 °; β = 107.94 ° and γ = 64.06 ° and two formula units per unit cell.