Marcasite (redirected from marcasitical)

marcasite (mär`kəsīt) or white iron pyrites, a mineral closely resembling and having the same chemical composition (FeS₂) as pyrite. It differs from pyrite in that it is paler in color, becomes darker upon oxidation, and crystallizes in the orthorhombic system. Twinned crystals resembling cockscombs (cockscomb pyrites) or spearheads (spear pyrites) are of common occurrence. The mineral occurs in marls, clays, and limestones in many parts of the world.

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marcasite

Iron sulfide mineral that forms pale bronze-yellow crystals; the name cockscomb marcasite refers to the shape of a common form of its crystals. Marcasite has the same chemical formula as pyrite (FeS₂) but a different internal (atomic) structure. It is less stable than pyrite, being easily decomposed, and is much less common.

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marcasite

a metallic pale yellow mineral consisting of iron sulphide in orthorhombic crystalline form used in jewellery. Formula: FeS₂

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marcasite [′mär·kə‚sīt]

(mineralogy)

FeS₂A pale bronze-yellow to nearly white mineral, crystallizing in the orthorhombic system; hardness is 6-6.5 on Mohs scale, and specific gravity is 4.89.

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Marcasite 

(also white iron pyrite), a mineral, a polymorphic variety of natural disulfide of iron, FeS₂. Marcasite crystallizes in the orthorhombic system. The luster is metallic. Of bronze-yellow color, which changes to gray along the crystal surface, the mineral forms spear-shaped, often complex, twin crystals, comb-like and round concretions, or sooty black masses (melnikovitemarcasite). Marcasite has a hardness of 6-6.5 on Mohs’ scale and a density of 4,850- 4,900 kg/m³. It usually forms from natural subacid solutions at temperatures lower than the temperature at which pyrite forms. Marcasite is found in hydrothermal deposits in association with pyrite, pyrrhotite, and other sulfides; it often replaces pyrrhotite in the oxidized zone of sulfide deposits. Marcasite occurring in sedimentary rocks is particularly widespread in Carboniferous deposits containing sand and clay, where it forms irregular nodular and concretionary formations. The mineral is used in the preparation of sulfuric acid.

REFERENCE

Mineraly; Spravochnik, vol. 1. Moscow, 1960.