Marcasite
- Speer gravel, gravel ridge, grit
- Liver gravel
- Water gravel
Marcasite is a commonly occurring mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the orthorhombic crystal system with the chemical composition FeS2, is therefore a chemical point of an iron ( II ) disulfide.
Marcasite is opaque in every shape and usually develops tabular, pyramidal or prismatic crystals, but also in the form of rosette -shaped, racemose or massive aggregates and radial- concretions occurs (especially in lignites). The color of marcasite varies from a rather dark bronze over brass yellow to tin white with occasional green tint. His stroke color is greenish gray to blackish.
The surfaces of fresh samples exhibit a metallic luster. Many marcasites be blunt but after some time in the air by weathering and may also call at this colorful colored.
Special Features
Marcasite is chemically less stable than the same pyrite and disintegrates in a period of several years. This sulfuric acid is formed and released from a typical odor of sulfur dioxide.
Etymology and history
Marcasite got its final name in 1845 by Wilhelm Ritter von Haidinger named after the Arabic or Moorish word مرقشيثا / marqašīṯā / flint ' for metallic - bronze-colored minerals. The name refers to the ability to make sparks when it is struck flint ( flint) or iron or steel.
Marcasite is more or less known by many names. Before it was recognized that marcasite and pyrite are two different minerals, both of which were often referred to in the literature as pyrite, marcasite parallel as. Mid-19th century it was recognized that the pyrite actually consisted of two different, albeit very similar minerals. Since then, pyrite and marcasite are run as independent minerals.
Because of its crystalline forms of marcasite also got various descriptive synonyms such as Binarkies or Binarit, leaves gravel, gray iron gravel, gravel ridge, Spear gravel and grit. As liver gravel (after Werner) massive, grapey were referred to kidney-shaped aggregates. The designation also outdated water gravel was interpreted by Henkel (1678-1744) as "white gravel ", but later picked up by Haussmann (1782-1859) again as a synonym for the marcasite.
Classification
In the now outdated but still in use 8th edition of the mineral classification by Strunz the marcasite belonged to the mineral class of " sulfides and sulfosalts " and then to the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 alone " Markasitgruppe " with the other members Anduoit, Ferroselit, Frohbergit, Iridarsenit, Kullerudit, Mattagamit and Omeiit formed as a namesake.
The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the marcasite also in the class of " sulfides and sulfosalts ," there, however, in the department of " metal sulfides with M: S ≤ 1: 2 ". This is also further subdivided by the exact molar ratio and the conditions prevailing in the interconnect metals, so that the mineral according to its composition in the subsection "M: S = 1: 2, with Fe, Co, Ni, PGE, etc. " is to be found where it is also named after him " Markasitgruppe " with the system no. 2.EB.10 forms. The group is, however, beside the marcasite only of the other members Ferroselit, Frohbergit, Kullerudit and Mattagamit.
The classification of minerals according to Dana assigns the marcasite in the class of " sulfides and sulfosalts " and there in the department of " sulfides". Here it is also named the " Markasitgruppe ( Orthorhombic: Pnnm ) " with the system no. 02:12:02 and the other members Ferroselit, Frohbergit, Mattagamit, Kullerudit, Omeiit, Anduoit, Löllingite, Seinäjokit, Safflorite, Rammelsbergite and Nisbit within the subdivision " sulfides - tellurides and selenides, including - with the composition AmBnXp, with (m n) p = 1: 2 to find ".
Modifications and varieties
Marcasite to pyrite is polymorphic, ie has the same composition but a different crystal system. Above 400 ° C, marcasite transforms to pyrite.
Education and Locations
Marcasite forms at low temperatures (in contrast to pyrite ) and is therefore usually near the surface, in brown coals, clays, marls, chalk; found in and on animal and plant fossils, but also in low temperature hydrothermal replacement deposits formed.
Exposed at the surface oxidizing conditions, weathered marcasite (faster than pyrite ) via several intermediates to iron oxide ( limonite or brown iron ore ) FeO · OH, where the sulfur is oxidized to sulfuric acid. Is accompanied by marcasite, calcite, dolomite, fluorite, galena, pyrite, pyrrhotite, quartz and sphalerite.
Worldwide, marcasite so far (as of 2012) are detected at around 3900 localities. In Germany, the mineral, especially in the Black Forest, Heidelberg, emperor chair, Kraichberg and Odenwald Baden -Wurttemberg joined; in several regions of Franconia, Lower Bavaria and the Upper Palatinate in Bavaria; Ruedersdorf in Berlin in Brandenburg; in many regions of Hesse, Lower Saxony, North Rhine -Westphalia and Saxony; at Friedland, Bad Doberan and Stralsund in Mecklenburg- Vorpommern; in the Eifel, Hunsrück on, the winning country and other regions in Rhineland -Palatinate and in some regions of the Saarland, Saxony -Anhalt, Schleswig-Holstein and Thuringia on.
In Austria, the mineral in Stadtschlaining in Burgenland, in Eichbüchl in Lower Austria, in the Lainzer tunnel in Vienna, can be detected in several regions of Tyrol and Upper Austria as well as in many regions of Carinthia, Salzburg and Styria.
In Switzerland, marcasite found on individual discovery locations of several cantons, including, inter alia in Graubünden, Solothurn, Ticino and Valais.
Even in rock samples from the Mid-Atlantic Ridge, Central Indian ridge and the East Pacific Rise was found marcasite.
Morphology
Euhedral crystals (crystals with complete formation of the self shape) are usually flat tabular to prismatic, often beilförmig. Often the crystals are twinned, often speerspitzige Much Linge in repetition, called " spear gravel " or " shingle ridge ". Also pseudomorphs of marcasite after pyrrhotite are known.
Crystal structure
Marcasite crystallizes in the orthorhombic space group Pnnm ( Raumgruppen-Nr. 58) with the lattice parameters a = 4.44 Å; b = 5.42 Å and c = 3.39 Å and two formula units per unit cell.
Use
As a raw material
As early as the Stone Age marcasite as well as pyrite was used to ignite the fire. However, marcasite is more suitable due to its massive structure to do so.
For the chemical industry is marcasite, especially if it occurs in some low - temperature hydrothermal deposits in larger amounts, broken down for the production of sulfuric acid.
As a gemstone
To gemstones marcasite is ground only of mineral collectors since the mineral in contrast to pyrite is less stable and slowly decomposes, the formation of sulfurous acid also makes it dangerous when direct skin contact. The also available in the jewelery trade pyrite is often mistakenly referred to as marcasite.