Pyrochlore

Pyrochlore is a commonly occurring mineral from the mineral class of " oxides and hydroxides " with the idealized chemical composition Ca2Nb2O7. It crystallizes in the cubic crystal system and often forms octahedral crystals with brown, red, greenish, orange, yellowish or black color.

Special Features

By substitution, numerous other features can be added into the crystal structure. The mineral may contain a large amount of rare earths, uranium and thorium. The radioactivity of the latter, the crystal lattice is often destroyed, whereby the mineral metamict and is optically isotropic.

Etymology and history

The name of pyrochlore (Greek πυρ pyr = fire, χλωρός chloros = green) goes on the back of the mineral property, after melting with salt of phosphorus before the blowpipe to a green glass to solidify.

Was first found pyrochlore 1826 Stavern in the Norwegian Vestfold and described by Friedrich Wöhler.

Classification

In the now outdated nomenclature of minerals by Strunz (8th Edition) pyrochlore still belongs to the Department of oxides with the molar ratio of metal: oxygen = 2: 3

The revision of the Strunz'schen Mineral classification in the 9th edition of the departments were partly redefined and divided precise. The pyrochlore is therefore now in the subdivision of " oxides with the molar ratio of metal: oxygen = 1: 2 and comparable with large (± medium-sized ) cations and layers of edge-sharing octahedra ."

The commonly used in English-speaking classification of minerals according to Dana assigns the pyrochlore also in the class of oxides and hydroxides, but there in the sub-division multiple oxides with Nb, Ta, and Ti; having the formula A2 ( B2O6 ) ( O, OH, F). He is the eponymous mineral " Pyrochlorgruppe ( pyrochlore subgroup; Nb > Ta, ( Nb Ta )> 2 (Ti) ) ".

Modifications and varieties

Due to the varied possibilities for substitution a number of modifications and varieties of the pyrochlore have been described. Koppit is cherry red in color and Ce -containing, the black Mutarait contains larger amounts of Zn and Fe in greenish brown Betafit can be found next to U significant amounts of rare earth elements and Pb.

Education and Locations

Pyrochlore is frequently associated with apatite, aegirine, zircon and rare earth minerals. It usually occurs in alkaline pegmatites and carbonatites at ( Koppit example in Emperor Chair / Baden- Württemberg).

As a frequent mineral pyrochlore formation is found at many localities, where so far (as of 2013) over 2300 localities are known.

In Germany the mineral occurred ( Munster, Oberwolfach, Sulzburg ) in Baden- Württemberg, in some places in the Bavarian Forest, in the Taunus ( mine Silbergaut and Phillipseck ) in Hesse, in several places in the resin ( Bad Loud Mountain, Clausthal in many places in the Black Forest -Zellerfeld, St Andrew Berg, Harzgerode ) from Lower Saxony to Saxony- Anhalt, in the Sauerland and winners district of North Rhine -Westphalia, in many places in the Eifel ( Laacher See, vineyards, Westerwald ), and in some places in Saxony and Thuringia.

In Austria they found pyrochlore so far mainly in Carinthia as, among other things in the area Friesach hut mountain and the Gurktaler Alps, but also in several places in Lower Austria ( hunchback world ), Salzburg ( Lungau), Styria and Tyrol's Inn Valley.

In Switzerland, you know the mineral so far only from the Upper Rhine Valley, from Chlitobel and from Murettopass in the canton of Grisons, from the Weisstannental in St Gallen and from Malcantone in Ticino.

Other localities lie include Afghanistan, Algeria, Angola, Argentina, Ethiopia, Australia, Bolivia, Brazil, Chile, China, the Democratic Republic of the Congo, Finland, France, French Guiana, French Polynesia, Gabon, Greece, Greenland, Guatemala, Guinea, Guyana, India, Iran, Ireland, Italy, Japan, Cameroon, Canada, Kazakhstan, Kenya, Kyrgyzstan, Luxembourg, Madagascar, Malawi, Malaysia, Mali, Morocco, Macedonia, Mexico, Mongolia, Mozambique, Myanmar, Namibia, New Zealand, Niger, Nigeria, North and South Korea, Norway, Pakistan, Paraguay, Peru, Poland, Portugal, Rwanda, Romania, Russia, Zambia, Saudi Arabia, Sweden, Zimbabwe, Slovakia, Somalia and Somaliland, Spain, South Africa, Swaziland, Tajikistan, Tanzania, Thailand, Turkey, Uganda, Ukraine, Hungary, Uzbekistan, Venezuela, the United Kingdom ( UK), the United States of America ( USA) and in Vietnam.

Also on the moon, more precisely in the rock samples brought back the probe Luna 24 from Mare Crisium and the mission Apollo 14 from the Fra Mauro highlands, pyrochlore could be detected.

Crystal structure

Pyrochlore crystallizes in the space group Fd3m cubic ( Raumgruppen-Nr. 227 ) with the lattice parameters a = 10.4 Å, and eight formula units per unit cell.

Use

Since the mineral contains a high proportion of niobium, it is for the aviation and aerospace industry of interest. Niobium alloys are considered as wear and corrosion resistant. Furthermore, the mineral is required for the preparation of superconductors.