The mineral marcasite, sometimes called white iron pyrite, is iron sulfide (FeS₂). Marcasite is often mistakenly confused with pyrite, but marcasite is lighter and more brittle. Specimens of marcasite often crumble and break up due to the unstable crystal structure, and it is this crystal structure that is the main difference between marcasite and pyrite. Though marcasite has the same chemical formula as pyrite, it crystallizes in a different crystal system, thereby making it a separate mineral. In jewelry, pyrite used as a gem is improperly termed "marcasite". This is wholly incorrect, as marcasite is never used as a gem. This article is about minerals in the geologic sense; for nutrient minerals see dietary mineral; for the band see Mineral (band). ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... In chemistry, a sulfide (sulphide in British) is a chemical compound or combination of sulfur with an oxidation number of -2, with another chemical element or a radical thereof. ... The mineral pyrite, or iron pyrite, is iron disulfide, FeS2. ... Rose des Sables (Sand Rose), formed of gypsum crystals In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... A chemical formula (also called molecular formula) is a concise way of expressing information about the atoms that constitute a particular chemical compound. ... GEM is an acronym for: Genetically Engineered Microorganism Global Electric Microcars Graphical Environment Manager — a windowing system created by Digital Research, Inc. ...

Two halves of a bowl of radiated marcasite from France.

Marcasite can be formed as both a primary or a secondary mineral. Image File history File links Download high resolution version (2329x1273, 1028 KB) A marcasite geode from my collection, taken by me on 3-13-05. ... Image File history File links Download high resolution version (2329x1273, 1028 KB) A marcasite geode from my collection, taken by me on 3-13-05. ...

As a primary mineral it forms nodules, concretions and crystals in a variety of sedimentary rock, such as at Dover, Kent, England, where it forms as sharp individual crystals and crystal groups, and nodules (similar to those shown here) in chalk. It can also be found in low-temperature hydrothermal veins. Two types of sedimentary rock: limey shale overlaid by limestone. ... Map sources for Dover at grid reference TR315415 Arms of Dover Borough Council This article is about the English port town. ... Kent is a county in England, south-east of London. ... Wikimedia Commons has media related to: England Travel guide to England from Wikitravel English language English law English (people) List of monarchs of England – Kings of England family tree List of English people Angeln (region in northern Germany, presumably the origin of the Angles for whom England is named) UK... The Needles, part of the extensive Southern England Chalk Formation Chalk is a soft, white, porous form of limestone composed of the mineral calcium carbonate. ... Hydrothermal circulation in the oceans is the passage of the water through mid-ocean Ridge (MOR) systems. ...

As a secondary mineral it forms by chemical alteration of a primary mineral such as chalcopyrite. On fresh surfaces it is pale yellow to almost white and has a bright metallic luster. It tarnishes to a yellowish or brownish color and gives a black streak. It is a brittle material that cannot be scratched with a knife. The thin, flat, tabular crystals, when joined in groups, are called "cockscombs." Chalcopyrite is a copper iron sulfide mineral that crystallizes in the tetragonal system. ... For the file system called Lustre, see Lustre (file system) Lustre (American English: luster) is a description of the way light interacts with the surface of a crystal, rock or mineral. ...

Marcasite may go through a condition known as "pyrite decay", in which a specimen slowly disintegrates into a white powder. Little is known about this detrimental condition. It only affects certain marcasite specimens seemingly at random, while other specimens remain unaffected. When a specimen goes through pyrite decay, the marcasite reacts with moisture in the air, the sulfur combining with water to produce sulfuric acid that attacks other sulfide minerals and mineral labels. It is most important to remove an afflicted specimen from other minerals to prevent this "disease" from spreading. General Name, Symbol, Number sulfur, S, 16 Chemical series nonmetals Group, Period, Block 16, 3, p Appearance lemon yellow Atomic mass 32. ... Sulfuric acid (British English: sulphuric acid), H2SO4, is a strong mineral acid. ...

Some research has suggested bacteria may aid and accelerate this process by literally 'eating' the marcasite. What is known is that samples with a rough surface tend to decay faster than those with bright, shiny faces, probably due to the greater surface area to react with water in the air, and also it's clear that samples kept in a dry environment (low humidity) are less likely to decay. Humidity is the concentration of water vapor in the air. ...

Other minerals often found associated with marcasite are galena, sphalerite, fluorite and calcite. Galena is a lead ore. ... Sphalerite sample Another sphalerite sample Sphalerite (ZnS) is a mineral that is the chief ore of zinc. ... Fluorite (also called fluor-spar) is a mineral composed of calcium fluoride, CaF2. ... Calcite from Brushy Creek Mine, Missouri, USA. The carbonate mineral calcite is a calcium carbonate corresponding to the formula CaCO3 and is one of the most widely distributed minerals on the Earths surface. ...

See also

• List of minerals