Skutterudite

• Smaltite
• Arséniure de cobalt
• Smaltine

Skutterudite is a rarely occurring mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the cubic crystal system with the idealized composition CoAs3, is so chemically seen a Cobaltarsenid. Since Skutterudite closely with nickel - skutterudite ( (Ni, Co, Fe) As 3 -x) is used, however, and forms a complete solid solution series, he usually also contains some nickel and iron, which can replace the Cobalt diadoch.

Skutterudite is opaque and usually develops cubic crystals and combinations, but also granular, massive, dendritic or skeletal aggregates. The color of fresh Skutterudite varies between tin white and steel gray. Visible crystal surfaces have a metallic luster. Under the influence of air, however, he runs after some time to green - up colorful color.

Etymology and history

Under his mining designation smaltite was Skutterudite since the Middle Ages known because it was used for the production of " smalt ". This name became Abraham Gottlob Werner in 1803 in his "Handbook of Mineralogy ". The word meat (of course) designated by one Johann Christoph Adelung in mining and metallurgy, among other metallic mixtures of unknown composition (eg: bell dish).

Due to the use to which the French mineralogist François Sulpice Beudant (also Smaltit occasionally written ) took the Arséniure de cobalt as Smaltine 1832 in his " Traité élémentaire de minéralogie " on.

His final name Skutterudite finally got the mineral in 1845 by Wilhelm Ritter von Haidinger, who named it after its type locality, the cobalt mines of Skutterud near Snarum and Modum in Norway.

Classification

Already in the now outdated but still in use 8th edition of the mineral classification by Strunz belonged Skutterudite for mineral class of " sulfides and sulfosalts " and then to the Department of " sulfides with the molar ratio of metal: sulfur, selenium, tellurium <1: 1 " where he the independent group II/D.29 formed together with Ferroskutterudit (IMA 2006-032 ), Gaotaiit, Iridisit, Kieftit and nickel - skutterudite.

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the skutterudite also in the class of " sulfides and sulfosalts ," there, however, in the department of " metal sulfides with M: S ≤ 1: 2 ". This department is also further subdivided by the exact molar ratio or the conditions prevailing in the interconnect metals, so that the mineral according to its composition in the subsection "M: S = 1: > 2 " is to find where it together with Ferroskutterudit, Kieftit and nickel - skutterudite the " Skutteruditgruppe " with the system no. 2.EC.05 forms.

The mainly common in English-speaking classification of minerals according to Dana assigns the skutterudite into the class of " sulfides and sulfosalts " and there in the department of " sulfide minerals ." Here he is with Kieftit, Ferroskutterudit and nickel - skutterudite in the " Skutteruditreihe " with the system no. 02:12:17 within the sub-division of " sulfides - tellurides and selenides, including - with the composition AmBnXp, with (m n): p = 1:2 " to find.

Modifications and varieties

In addition to its original meaning as a synonym of the name Skutterudits Smaltin or Smaltit is now used as a term for a variety of the mineral arsenic poorer.

Smaltite is also massive, disseminated and in varied clustered aggregates, is tin white to gray, sometimes brightly colored red or run by incipient decomposition to cobalt bloom on the surface.

In certain varieties of the content of nickel is so significant that the same will be more likely attributed to the nickel - skutterudite, while the iron-rich rather than varieties of Safflorite (obsolete: Gray smaltite, iron cobalt gravel) apply. An up to 4 percent bismuth ( bismuth ) -containing mineral is distinguished as bismuth cobalt gravel.

Education and Locations

Skutterudite formed in moderate to severe hydrothermal veins, where he associated with most other nickel -cobalt sulphides such as Nickeline, cobaltite and arsenopyrite, but also with native bismuth and silver, barite, calcite, quartz and / or siderite found is.

As a rather rare mineral formation Skutterudite at different sites can be abundant in some cases, overall it is not very common. So far (as of 2011) are regarded as known a little more than 400 localities. Apart from its type locality Skutterud the mineral in Norway yet been entered in the " Lerestvedt Mine" at Øyestad in the municipality of Arendal and silver mining area around Kongsberg on.

In Germany Skutterudite found so far mainly in the Black Forest in Baden -Württemberg and in the Ore Mountains in Saxony, but also in several places in Franconia and Wölsendorf in Bavaria, in a number of mines in the Odenwald and in Richelsdorfer mountains in Hesse, in many places in the Harz from Lower Saxony to Saxony- Anhalt, in the Bergische Land and winners district of North Rhine -Westphalia, at several sites in Imsbach, at Landsberg near Obermoschel, Rockhausen and Bürdenbach in Rhineland -Palatinate and Thuringia in Bad Lobenstein, Ronneburg and Kamsdorf on.

In Austria, the mineral so far at Erzberg hut in Carinthia, the zinc wall in Obertalbachtal ( Schladming Tauern ) was found in Styria and in several places in Salzburg.

At Swiss localities have so far only Böttstein in Canton Aargau and various mines in Ayertal and the municipality in the canton of Valais Turtmann known.

Other localities lie include Afghanistan, Argentina, Australia, Bolivia, Chile, China, France, Greenland, Ireland, Italy, Japan, Canada, Madagascar, Mexico, Morocco, Poland, Portugal, Russia, Sweden, Slovakia, Spain, South Africa, South Korea, the Czech Republic, the United Kingdom ( UK) and the United States (USA).

Crystal structure

Skutterudite crystallized cubic space group Im 3 ( Raumgruppen-Nr. 204 ) with the lattice parameters a = 8.31 Å, and eight formula units per unit cell.

Use

Skutterudite was until the end of the 19th century an important cobalt and nickel ore for blue color preparation, with nickel and white arsenic (III ) oxide ( arsenic ) was obtained as a byproduct. Meanwhile, these metals are mainly composed of nickel magnetic gravels ( mixture of pentlandite and pyrrhotite ) and laterites.

Skutterudites are traded as candidates for efficient thermoelectric converter, with which about heat in the exhaust system of a car can be converted directly into electricity, however, are contrary to the considerable technical problems.