Raspite

Raspit is a rarely occurring mineral with the chemical composition of α - PbWO4. It crystallizes in the monoclinic crystal system and would alone its chemical formula assigned to the lead tungstates by more. However, due to its crystal structure, it belongs in the Strunz'schen mineral classifications for mineral class of " oxides and hydroxides " with the molar ratio of metal: oxygen = 1: 2 (and similar ).

Raspit is translucent and developed only small, tabular, along striped crystals and twins from a few millimeters in length, pale yellow to yellowish brown or gray in color with yellowish white line color. The crystal surfaces show a diamond-like luster.

Special Features

At a temperature of about 410 ° C, transforms into Raspit Stolzit.

Etymology and history

The mineral was first discovered in 1896 had obtained in two samples from the collection of the Vienna Natural History Museum (formerly the Imperial Natural History Museum courtyard ), the Baron Heinrich Foullon of Norbeeck ( 1850-1896 ) Broken Hill (Australia). Baron of Norbeeck suspected on the sample a new mineral, for which he proposed the name Raspit, according to the German emigrants Charles Rasp (1846-1907). This had discovered the deposits in and around Broken Hill and recognized their economic importance.

Analyzed and described the mineral in 1897 by Karl Hlawatsch ( Carl Hlawatsch, 1870-1947 ), Baron of Norbeecks was suggested name took over.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the Raspit belonged to the mineral class of " oxides and hydroxides " and then to the Department of " oxides with the molar ratio of metal: oxygen = 1: 2 ( MO2 and related compounds ) ", where he along with fergusonite - (Ce), fergusonite - (Nd), fergusonite - (Y), fergusonite - beta - (Ce), fergusonite - beta - (Nd), fergusonite - beta - (Y), Formanit ( Y) and Iwashiroit (Y ), the " fergusonite - series" with the system number. IV/D.24 formed.

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the Raspit also in the department of " oxides with the molar ratio of metal: oxygen = 1: 2 and comparable " one. However, this is further divided according to the relative size of the involved cations and the crystal structure, so that the mineral according to its composition in the subsection "With large (± medium-sized ) cations; Chains of edge-sharing octahedra "can be found, where it forms the unnamed group 4.DG.20 the only member.

The mainly common in English-speaking classification of minerals according to Dana assigns the Raspit other hand, in the class of " phosphates, arsenates and vanadates " and there in the department of " molybdates and tungstates " one. Here he is " XO4 anhydrous molybdates and tungstates with A" to find the only member of the unnamed group 48.01.04 within the subdivision.

Modifications and varieties

The connection PbWO4 is dimorphic and is found in nature in addition to the monoclinic crystallized as tetragonal Raspit still crystallizing Stolzit ago.

Education and Locations

Raspit formed secondarily in the oxidation zone of tungsten-containing hydrothermal deposits. Accompanying minerals may include Alumotungstit and Ferritungstit ( varieties of Hydrokenoelsmoreit ) Cuprotungstit, Stolzit and Yttrotungstit

A rare mineral formation Raspit could be detected only in a few places, where so far (as of 2013) are about 20 localities known as. Apart from its type locality Broken Hill mineral in Australia could only still in the " Cordillera Mine" at Kangaloolah ( Georgiana County, New South Wales ) are found.

The only known locality in Germany is the Clara mine in Oberwolfach.

Other previously known localities include Sumidouro in the Brazilian state of Minas Gerais; the Otish Mountains uranium deposit in the near James Bay ( Baie- James ) in Canada; an unnamed iron -germanium deposit in Nanyue (Hengyang ) in China; Échassières ( Allier ), Meymac ( Correze ) and Compolibat ( Aveyron ) in France; Gyojayama near Kameoka on the Japanese island of Honshu; the " San Antonio Mine" at Santa Eulalia (Chihuahua ) and a Tin Lode at Cerro de Estaño east of Guanajuato in Mexico; the Erongo Mountains in Namibia; Estorãos (Ponte de Lima) in Portugal; Gifurwe in the Northern Province of Rwanda and the Carr Canyon near Hartford and Tombstone in Cochise County of the U.S. state of Arizona.

Crystal structure

Raspit crystallizes in the monoclinic space group P21 / a ( Raumgruppen-Nr. 14) with the lattice parameters a = 13.56 Å; b = 4.98 Å; c = 5.56 Å and 107.6 ° and β = 4 formula units per unit cell.

The crystal structure of Raspit consists of edge-sharing [ WO6 ] octahedra that form parallel to the b axis zigzag chains are connected by lead atoms.