Wavellite

Wavellite, interchangeably also known as Fischerit and Lasionit, is a rarely occurring mineral from the mineral class of " phosphates, arsenates and vanadates ." It crystallizes in the orthorhombic crystal system with the chemical composition Al 3 [ (OH, F) 3 | ( PO4 ) 2] · 5H2O and developed predominantly hemispherical to spherical, grape-like and radial- mineral aggregates up to four centimeters in diameter, but also crusty coatings and rarely also prismatic, isometric to elongated crystals.

Special Features

Reiner Wavellite is colorless or white. However, it can be colored by foreign admixtures yellowish or greenish to bluish, with the greenish coloration predominate. Also zonal staining similar to some minerals of the tourmaline are possible.

Is Wavellite before the blowtorch infusible and insoluble in hydrochloric acid.

Etymology and history

Was first found in 1805 by British physicist William Wavellite Wavell († 1829) and described by William Babington, who named the mineral after its discoverer.

Beginning of the 19th century was at Nishne Tagilsk in the Urals a new variety of Wavellite found that one initially considered an independent mineral and designated by Gotthelf Fischer von Waldheim ( 1771-1853 ) as Fischerit. The only description of R. Hermann after the Fischerit consisted of transparent, crystalline crusts and short prismatic crystals from grass-green to olive-green and chipping green color, which were found on the clefts of sandstone and Toneisenstein. For subsequent analyzes, however, it turned out that Fischerit with Wavellite is identical. Slavik after the Fischerit was designated as Uhligit.

Classification

In the old ( 8th edition ) and new classification of minerals according to Strunz ( 9th edition ) of the Wavellite belongs to the department of " hydrous phosphates with foreign anions ." The new Strunz'sche Mineral classification divided here, however, precisely according to the relative size of the cations and the molar ratio of the additional anions for phosphate, arsenate or Vanadatkomplex ( RO 4 ). Accordingly, the mineral is now in the subsection "With only medium-sized cations, (OH, etc.): RO 4 = 1:1 and < 2:1 " to find out where he along with Allanpringit the " Wavellite group " with the system No. 8.DC.50 forms.

The more commonly used in English-speaking classification of minerals according to Dana assigns the Wavellite also in the class of " phosphates, arsenates and vanadates " and then in the Department of " water -containing phosphates, etc., with hydroxyl" and here he finds himself together with Allanpringit in the " Wavellitgruppe " with the system number. 42.10.02 within the subdivision " Hydrated Phosphates, etc., with hydroxyl or halogen with (AB ) 3 ( XO4 ) 2 Zq • x (H2O) "

Education and Locations

Wavellite forms as a secondary mineral in metamorphic rocks and phosphate -containing deposits, less often by hydrothermal processes. However, formation of a metamorphic is also possible. Wavellite is found mainly on fractures, particularly of sandstone, clay and chert, but also iron stones, granite, mica schist.

So far Wavellite was at 285 archaeological sites discovered (as of 2009), including, inter alia, in some regions of Australia; Liège, Luxembourg and Namur in Belgium; Departamento Oruro, Potosí Department and Department of Santa Cruz in Bolivia; Bavaria ( Fichtelgebirge, Upper Palatinate Forest ), Hesse, North Rhine -Westphalia (Sauerland ), Rhineland -Palatinate (Westerwald ), Saxony -Anhalt (Harz ), Saxony (Erzgebirge) and Thuringia ( Gera, Vogtland) in Germany; several regions in France; England and Wales in the United Kingdom; some counties in Ireland; Katanga in the Congo; Jordansmühl / Silesia in Poland; Bohemia ( Cerhovice ) and Moravia in the Czech Republic; and Arizona, Arkansas, Colorado, Nevada, Pennsylvania and many other regions of the United States.

Crystal structure

Wavellite crystallizes in the orthorhombic crystal system, space group Pcmn ( Raumgruppen-Nr. 62) with the lattice parameters a = 9.621 Å, b = 17.3630 Å and c = 6.994 Å and six formula units per unit cell.