Marcasite
| Marcasite | |
|---|---|
 |
|
| General and classification | |
| other names |
|
| chemical formula | FeS 2 |
|
Mineral class (and possibly department) |
Sulfides and sulfosalts |
|
System no. to Strunz and to Dana |
2.EB.10a ( 8th edition : II / D.20) 02.12.02.01 |
| Similar minerals | Pyrite |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 / m 2 / m 2 / m |
| Space group | Pnnm (No. 58) |
| Lattice parameters | a = 4.44 Å ; b = 5.42 Å; c = 3.39 Å |
| Formula units | Z = 2 |
| Frequent crystal faces | {001} |
| Twinning | often twinned according to (110) |
| Physical Properties | |
| Mohs hardness | 6 to 6.5 ( VHN 200 = 915-1099) |
| Density (g / cm 3 ) | measured: 4.887; calculated: 4.875 |
| Cleavage | imperfect after {110} |
| Break ; Tenacity | uneven, brittle |
| colour | bronze-colored to brass-yellow to tin-white, occasionally a green cast and brightly colored tarnishing |
| Line color | greenish gray to blackish gray |
| transparency | opaque |
| shine | Metallic luster |
| magnetism | magnetic after heating |
| Other properties | |
| Special features | Sparking, sulfur dioxide odor on decomposition |
Marcasite is a frequently occurring mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the orthorhombic crystal system with the chemical composition FeS 2 , so it is chemically an iron (II) disulfide .
Marcasite is opaque in every form and usually develops tabular, pyramidal or prismatic crystals , but also occurs in the form of rosette-shaped, grape-like or massive aggregates and radial concretions (especially in lignite). The color of marcasite varies from a rather dark bronze tone to brass yellow to pewter white with an occasional green cast. Its stroke color is greenish gray to blackish gray.
The surfaces of fresh samples have a metallic sheen . Many marcasites become dull but after some time in the air by weathering and can thereby also multicolored start .
Etymology and history
Marcasite was assigned its German name, which is still valid today, in 1845 by Wilhelm Ritter von Haidinger . The underlying Latin marchasita comes from Arabic or Moorishمرقشيثا / marqašīṯā / 'flint', which up into modern times was metallic (bronze-colored) ore minerals such as B. pyrite or marcasite, but also galena ( marchasita plumbea ) or gray skewer luster . The name refers to the ability to give off sparks when struck on 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 were often referred to in the literature as pyrites , also referred to as marcasite. In the mid-19th century it was discovered that pyrites actually consisted of two different, albeit very similar, minerals. Since then, pyrite and marcasite have been listed as separate minerals.
Because of its crystalline forms of marcasite also received various descriptive synonyms as Binarkies or Binarit , leaves gravel , gray iron pyrites , comb gravel , spear gravel and grit . As liver gravel (after Werner) massive, grape-like to kidney-shaped aggregates were called. The also outdated term water gravel was interpreted by Henkel (1678–1744) as “white gravel”, but was later taken up again as a synonym for marcasite by Hausmann (1782–1859).
classification
Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the marcasite belonged to the mineral class of "sulfides and sulfosalts" and there to the department of "sulfides with the molar ratio metal: sulfur, selenium, tellurium <1: 1" where he named the "marcasite group" with the system no. II / D.20 and the other members anduoite , ferroselite , frohbergite , hastite , iridarsenite , kullerudite , mattagamite and omeiite , which was discredited in 2009 .
In contrast , the 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), classifies the marcasite in the category of “Metal sulfides with M: S ≤ 1: 2”. This is further subdivided according to the exact molar ratio and the predominant metals in the compound, so that the mineral can be found in the sub-section "M: S = 1: 2, with Fe, Co, Ni, PGE etc." according to its composition , where the "marcasite group" named after him with the system no. 2.EB.10a forms. In addition to the marcasite, the group only consists of the other members ferroselite, frohbergite, kullerudite and mattagamite.
The systematics of minerals according to Dana also assigns the marcasite to the class of "sulfides and sulfosalts" and there in the department of "sulfide minerals". Here he is also the namesake of the " marcasite group (Orthorhombic: Pnnm) " with the system no. 02.12.02 and the other members Ferroselite, Frohbergite, Mattagamite, Kullerudite, Omeiite, Anduoite, Löllingite , Seinäjokit , Safflorite , Rammelsbergite and Nisbit within the subsection “Sulphides - including selenides and tellurides - with the composition A m B n X p , with (m + n): p = 1: 2 “.
Crystal structure
Marcasite crystallizes orthorhombically in the space group Pnnm (space group no. 58) with the lattice parameters a = 4.44 Å ; b = 5.42 Å and c = 3.39 Å and 2 formula units per unit cell .
properties
morphology
Idiomorphic crystals (crystals with a complete development of their own shape) are mostly tabular to flat prismatic, often ax-shaped. Often the crystals are twinned, often spear-pointed Viellings in repetition, called "spear gravel" or "comb gravel". Also pseudomorphic of marcasite by pyrrhotite are known.
Chemical and physical properties
Marcasite is less stable than chemically identical pyrite and decays over a period of several years. Here is sulfuric acid formed and released a typical odor of sulfur dioxide. When heated to over 400 ° C, marcasite transforms monotropically into pyrite.
Modifications and varieties
Marcasite is polymorphic to pyrite, so it has a different crystal system with the same composition .
Education and Locations
Marcasite forms at low temperatures (in contrast to pyrite) and is therefore mostly near the surface of the earth, in lignite, clays, marls, chalk; to be found in and on animal and plant fossils, but also in displacement deposits formed hydrothermally at low temperatures .
When exposed to oxidizing conditions on the earth's surface, marcasite (faster than pyrite) weathers through several intermediate stages to form iron oxide hydrate ( limonite or brown iron ore) FeO · OH, whereby the sulfur is oxidized to sulfuric acid. Marcasite is accompanied by calcite , dolomite , fluorite , galena , pyrite , pyrrhotite, quartz and sphalerite .
So far (as of 2012), marcasite has been found at around 3900 sites worldwide. In Germany the mineral occurred mainly in the Black Forest , Heidelberg , Kaiserstuhl , Kraichberg and Odenwald in Baden-Württemberg; in several regions of Franconia , Lower Bavaria and the Upper Palatinate in Bavaria; in Rüdersdorf near Berlin in Brandenburg; in many regions of Hesse , Lower Saxony , North Rhine-Westphalia and Saxony ; near Friedland , Bad Doberan and Stralsund in Mecklenburg-Western Pomerania; in the Eifel , Hunsrück , Siegerland and other regions in Rhineland-Palatinate as well as in some regions of Saarland , Saxony-Anhalt , Schleswig-Holstein and Thuringia .
In Austria, the mineral could be detected near Stadtschlaining in Burgenland, near Eichbüchl in Lower Austria, in the Lainzer Tunnel in Vienna, in several regions of Tyrol and Upper Austria as well as in many regions of Carinthia , Salzburg and Styria .
In Switzerland, marcasite was found at individual sites in several cantons , including in Graubünden, Solothurn, Ticino and Valais.
Marcasite was also found in rock samples from the Mid-Atlantic Ridge , Central Indian Ridge and East Pacific Ridge .
use
As a raw material
Like pyrite, marcasite was used to ignite fires as early as the Stone Age . However, marcasite is better suited for this due to its massive structure.
For the chemical industry, marcasite is mined to produce sulfuric acid, especially if it occurs in large quantities in some low-temperature hydrothermal deposits.
As a gem
To precious stones marcasite is ground only of mineral collectors, since the mineral unlike pyrite is less stable and slowly decays, the formation of sulfur dioxide also makes it dangerous when direct skin contact. The pyrite, which is also available in jewelry stores, is often incorrectly referred to as marcasite.
See also
literature
- Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 461–463 (first edition: 1891).
- Petr Korbel, Milan Novák: Mineral Encyclopedia (= Villager Nature ). Nebel Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 46 .
- Martin Okrusch, Siegfried Matthes: Mineralogy. An introduction to special mineralogy, petrology and geology . 7th, completely revised and updated edition. Springer, Berlin [a. a.] 2005, ISBN 3-540-23812-3 , pp. 39 .
- Walter Schumann: Precious stones and gemstones. All kinds and varieties. 1900 unique pieces . 16th revised edition. BLV Verlag, Munich 2014, ISBN 978-3-8354-1171-5 , pp. 178, 238 .
Web links
- Mineral Atlas: Marcasite (Wiki)
- Mineral Lexicon - Marcasite
- Gemstone etiquette - marcasite
- RRUFF Database-of-Raman-spectroscopy - Marcasite (English)
- American-Mineralogist-Crystal-Structure-Database - Marcasite (English)
- Webmineral - Marcasite (English)
Individual evidence
- ^ A b c Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 106 .
- ↑ a b Marcasite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 61 kB ; accessed on August 27, 2017]).
- ↑ Udo Benzenhöfer : Johannes' de Rupescissa Liber de consideratione quintae essentiae omnium rerum, German. Studies on Alchemia medica from the 15th to the 17th century with a critical edition of the text (= Heidelberger studies of natural history of the early modern period . No. 1 ). Steiner, Stuttgart 1989, ISBN 978-3-515-05388-4 , pp. 187 .
- ↑ GeoMontanus - The Minerals of Rescheid ( Memento of the original from June 29, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Hans Lüschen: The names of the stones. The mineral kingdom in the mirror of language . 2nd Edition. Ott Verlag, Thun 1979, ISBN 3-7225-6265-1 , p. 272 .
- ↑ Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p. 326-327 .
- ↑ Mindat - Marcasite (English)
- ↑ Find location list for marcasite in the Mineralienatlas and Mindat
