Mackinawite
Mackinawite is a mineral from the mineral class of " sulfides and sulfosalts ," which can be partly abundant in various localities, but overall is not widespread. It crystallizes in the tetragonal crystal system with the chemical composition (Fe, Ni) 9S8 and sometimes developed thin, tabular crystals up to 1 mm size of bronze or white - gray color. Much more often, however, it is found in the form of tiny, irregular tinsel or inclusions in chalcopyrite or pentlandite.
Etymology and history
Mackinawite was the first time in 1963 by H.T. Evans, Charles Milton and found others in the Mackinaw Mine, Snohomish County in the U.S. state of Washington. The mineral was named after its type locality.
Mackinawite was formerly often confused with the very similar looking Valleriit. The similarity and the spread are so similar that the two minerals were considered a mineral. However Valleriit has a different chemical composition and is also softer than mackinawite.
Classification
In the now outdated but still in use 8th edition of the mineral classification by Strunz the Mackinawite belonged to the mineral class of " sulfides and sulfosalts " and then to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 formed a distinct group with Godlevskit and Kharaelakhit.
The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the Mackinawite 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 single member of the unnamed group forms 2.CC.25.
The mainly common in English-speaking classification of minerals according to Dana assigns the mackinawite into the class of " sulfides and sulfosalts " and there in the department of " sulfide minerals ." Here he is the only member of the unnamed group 02:07:02 within the sub-division of " sulfides - with the composition AmBnXp, with (m n) - including selenides and tellurides: p = 9:8 " to find.
Education and Locations
Mackinawite formed hydrothermally in mineral deposits and during the serpentinization of peridotite. Also in Gewässerschlämmen under reducing conditions, mackinawite may form, with a participation of sulfate - reducing bacteria is suspected. In addition, it is found rarely in some meteorites, the carbonaceous chondrites.
Overall, mackinawite has so far (as of 2011) are detected at around 230 localities. In Germany the mineral occurred in Hagendorf ( Waidhaus ) in Bavaria and at the Rammelsberg in Saxony.
In Austria, mackinawite was on Hüttenberger Erzberg and the Lamprechtsberg in Carinthia; in the leak Bachgraben in Habachtal, on Murwinkel and Schwarzleograben in Salzburg; at Voitsberg in Styria and in the Tyrolean Inn Valley.
In Switzerland, the mineral was found in Palagnedra in the Ticino Canton in the Binn Valley and in Hérens in the canton of Valais.
Other localities lie in Egypt, Algeria, Argentina, Australia, Brazil, Bulgaria, China, Finland, France, Greenland, India, Indonesia, Italy, Canada, Kazakhstan, Japan, Morocco, Mauritania, Nigeria, Norway, Oman, Pakistan, Peru, Poland, Portugal, Romania, Russia, Sweden, Senegal, Zimbabwe, Spain, South Africa, Turkey, the United Kingdom ( UK) and the United States and Cyprus.
Even in rock samples from the Red Sea ( Atlantis II Deep ) and outside the earth on the moon Mackinawite could be detected.
Crystal structure
Mackinawite crystallizes in the tetragonal crystal system, space group P 4/nmm, the lattice parameters a = 3.67 Å and c = 5.03 Å and two formula units per unit cell.