Pyrrhotite

• Pyrrhotite

Pyrrhotite outdated, also known as pyrrhotite, is a commonly occurring mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes depending on structure type in the monoclinic or hexagonal crystal system with the chemical composition of FeS to Fe11S12. Other sources, such as, among others, by the International Mineralogical Association (IMA ) published list of minerals also give the formula of the most common modification pyrrhotite -4M again with Fe7S8.

Since the iron content in the formula may vary slightly for structural reasons, the generalized formula Fe1 - xS with x = 0 to 0.17 is often quoted. The mineral is thus a chemical point of an iron ( II ) sulfide with a slight under-saturation of iron.

Pyrrhotite is opaque in every shape and usually develops tabular, pyramidal or prismatic crystals, but also massive aggregates of yellow to bronze color tombakbrauner in gray black stroke color. In air, pyrrhotite runs fast matt brown, rarely colorful iridescent, at.

Special Features

Pyrrhotite is usually ferromagnetic. Before the blowpipe it melts to a black magnetic mass and in nitric acid and hydrochloric acid it is only sparingly soluble.

Etymology and history

Originally, the mineral was ( briefly pyrrhotite ) primarily known as Magnetic gravel, as it is also found in the mineralogical records of Abraham Gottlob Werner in 1789. Ernst Friedrich Glocker described him in 1839 as Magneto pyrite. In other languages ​​, there are corresponding variations of these old names, so including France ( Fer Sulfure magnetic ), England (Magnetic sulfuret of iron ) and Spain ( Pyrita magnetica ).

The current valid name to the mineral pyrrhotite received in 1835 by August Breithaupt, the " fire- colored" for named it after the Greek word πνρρός ( pyrrhos ).

Classification

In the now outdated but still in use classification of minerals ( 8th Edition ) by Strunz was one of pyrrhotite to mineral class of " sulfides and sulfosalts " and then to the Department of " sulfides with a molar ratio of metal: sulfur, selenium, tellurium = 1: 1 "where he the unnamed group II/C.19 formed together with Achavalit, Heideit, Jaipurit, Modderit, Smythit, troilite and Westerveldit.

The valid since 2001 and used by the IMA 9th edition of the Strunz'schen Mineral classification assigns the pyrrhotite also in the class of " sulfides and sulfosalts " and there in the department of "Metal Sulfides, M: S = 1: 1 ( and similar ) " a. This division, however, is further subdivided according to the conditions prevailing in the interconnect metals, so that the mineral according to its composition in the subdivision " with nickel ( Ni ), iron ( Fe), cobalt ( Co ), etc. " can be found, where it acts as named the " Pyrrhotingruppe " with the system no. Forms 2.CC.10 and the other members Smythit and troilite.

The mainly common in English-speaking classification of minerals according to Dana assigns the pyrrhotite in the class of " sulfides and sulfosalts " and there in the department of " sulfide minerals " one. Here he is with Smythit in the unnamed group 02:08:10 within the sub-division of " sulfides - tellurides and selenides, including - with the composition AmBnXp, with (m n ): 1: p = 1" to find.

Education and Locations

Pyrrhotite formed predominantly magmatic liquid in intra magmatic sulphide deposits as well as in leading sulfide pegmatites, where it usually occurs in paragenesis with other sulfides such as, among others, chalcopyrite, marcasite, pentlandite and pyrite.

In addition, pyrrhotite is also in the hydrothermal post-phase of pneumatolytic replacement deposits and other hydrothermal ore deposits with higher formation temperature. Here can be found next to chalcopyrite and pyrite, among others yet galena, iron-rich sphalerite, arsenopyrite and stibnite as accompanying minerals. In regionalmetamorph converted rocks of Katazone pyrite in pyrrhotite is usually transferred.

In sediments and sedimentary rocks is pyrrhotite found but rarely, because it is easily decomposed in the oxidation zone.

As a frequent mineral formation could pyrrhotite already at over 6600 localities (as of 2012) are detected. Large deposits with industrial importance include Greater Sudbury (Ontario) in Canada and Talnach (English Talnakh ) in Russia.

Known due to exceptional pyrrhotite finds are mainly Trepča in Kosovo and Dalnegorsk in Russia, where tabular crystals up to 30 cm in diameter have been found. In Santa Eulalia (Chihuahua ) in Mexico were up to 15 cm large crystals to light and Chiuzbaia ( Baia Sprie ) and Cavnic in Romania found themselves 11-15 centimeters large crystals. Other known localities with good pyrrhotite findings of usually several centimeters in size include the " Morro Velho Mine" in Nova Lima ( Minas Gerais ) in Brazil and the "Blue Bell Mine" in the Canadian province of British Columbia.

In Germany, the mineral found so far at many localities in Baden- Württemberg (Black Forest, Emperor chair, Kraichgau, Odenwald) and Bavaria ( Bavarian Forest, Fichtelgebirge, Bavaria), at Niederlehme in Brandenburg, in many places in Hesse ( Dillenburg, Fulda, Odenwald ) in Adelebsen, Peine and the Harz Mountains in Lower Saxony, in many places in North Rhine -Westphalia and Rhineland -Palatinate (Eifel, Sauerland, Seven Mountains, winner of the country), at Reimsbach in Saarland, near Gernrode, Neudorf, Stolberg and Tarthun in Saxony -Anhalt in many places in Saxony (Erzgebirge, Black mountain, Upper Lusatia Vogtland), at the crest of the mountain at Joldelund in Schleswig -Holstein and in Drosen and Loitsch in Thuringia.

In Austria pyrrhotite occurred in the areas around Friesach - hut mountain, Hohe Tauern, Gail Valley Alps, Carnic Alps, Gurktaler Alps and the Kor especially in Carinthia and Salzburg. Furthermore, it was also in Burgenland on Pauliberg and Bernstein, at several sites in Lower Austria as, among others, in the Waldviertel, Styria ( Fischbacher Alps, Koralpe ), in North and East Tyrol, Upper Austria ( Upper Austria, Windischgarsten ) and in Vorarlberg (sub Klien, Montafon ) on.

In Switzerland, was the mineral at several localities in de cantons of Bern, Graubünden ( anterior Rhine valley), Ticino (Lake Maggiore, Maggia Valley ), Uri ( Reusstal ) and especially Wallis ( Binn valley ) are found.

Also, in some mineral samples from the Mid-Atlantic Ridge, the East Pacific ridge and the Red Sea ( Atlantis II Deep ) and in comet Wild 2 dust of pyrrhotite could be detected.

Crystal structure

Are from pyrrhotite, including recognized as an independent mineral Troilits with the ideal composition FeS and hexagonal symmetry, currently six different polytypes known: the hexagonal high-temperature modifications of pyrrhotite, however, are stable only above 300 ° C.

• Pyrrhotite -4M ( Fe7S8 ) crystallizes in the monoclinic space group C2 / a with lattice parameters a = 11.90 Å; b = 6.87 Å, c = 22.88 Å and β = 90.1 ° and 8 formula units per unit cell.

• Pyrrhotite -6M ( Fe11S12 ) crystallizes in the monoclinic space group not defined in some detail with the lattice parameters a = 6.90 Å; b = 11.95 Å, c = 34.52 Å and β = 90.0 ° and 8 formula units per unit cell.

• Pyrrhotite -5H ( Fe9S10 ) crystallizes in hexagonal space group not defined in some detail with the lattice parameters a = 6.89 Å and c = 28.67 Å and four formula units per unit cell.

• Pyrrhotite -7H ( Fe9S10 ) crystallizes in hexagonal space group not defined in some detail with the lattice parameters a = 6.89 Å and c = 40.15 Å and 56 formula units per unit cell.

• Pyrrhotite - 11H ( Fe10S11 ) crystallizes in hexagonal space group not defined in some detail with the lattice parameters a = 6.90 Å and c = 63.22 Å, and eight formula units per unit cell.

Except for the troilite, which is almost exclusively found in meteorites, all other polytypes are of iron ( Fe) understaffed, which is due to vacancies in the crystal lattice.

Use

Pyrrhotite is occasionally used for local accumulation than iron ore, but more often associated with pentlandite as nickel ore. In addition, pyrrhotite occasionally serves as a raw material for the production of rouge, a well-known, still estimated means for fine polishing of metals and glasses, and for the production of green vitriol use.