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Pyrite and marcasite commonly occur as replacement pseudomorphs after fossils in black shale and other sedimentary rocks formed under reducing environmental conditions. [58] Pyrite is common as an accessory mineral in shale, where it is formed by precipitation from anoxic seawater, and coal beds often contain significant pyrite. [59]
The group is named for its most common member, pyrite (fool's gold), which is sometimes explicitly distinguished from the group's other members as iron pyrite. Pyrrhotite (magnetic pyrite) is magnetic, and is composed of iron and sulfur , but it has a different structure and is not in the pyrite group.
Pyrite, a sulfur-bearing mineral that forms in some ocean sediments, usually has relatively low δ 34 S values due to the indirect role of biology in its formation. Microbial dissimilatory sulfate reduction (MSR), an energy-yielding metabolism performed by bacteria in anoxic environments, is associated with an especially large fractionation ...
The mineral marcasite, sometimes called "white iron pyrite", is iron sulfide (FeS 2) with orthorhombic crystal structure. It is physically and crystallographically distinct from pyrite, which is iron sulfide with cubic crystal structure. Both structures contain the disulfide S 2 2− ion, having a short bonding distance between the sulfur atoms.
After deposition, sediments are compacted as they are buried beneath successive layers of sediment and cemented by minerals that precipitate from solution. Grains of sediment, rock fragments and fossils can be replaced by other minerals (e.g. calcite, siderite, pyrite or marcasite) during diagenesis.
These soils contain iron sulfide minerals (predominantly as the mineral pyrite) and/or their oxidation products. In an undisturbed state below the water table, acid sulfate soils are benign. However, if the soils are drained, excavated or otherwise exposed to air, the sulfides react with oxygen to form sulfuric acid. [1]
Wolframite is an iron, manganese, and tungstate mineral with a chemical formula of (Fe,Mn)WO 4 that is the intermediate mineral between ferberite (Fe 2+ rich) and hübnerite (Mn 2+ rich). [4] Along with scheelite , the wolframite series are the most important tungsten ore minerals.
An evaporite (/ ɪ ˈ v æ p ə ˌ r aɪ t /) is a water-soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. [1] There are two types of evaporite deposits: marine, which can also be described as ocean deposits, and non-marine, which are found in standing bodies of ...