Greigite is an ironsulfide mineral with formula:Fe2+Fe3+2S4. It is a magnetic sulfide analogue of the iron oxide magnetite. Greigite occurs as microscopic (< .03 mm) isometric hexoctahedral crystals and as minute sooty masses. It is a bio-mineral produced by and found in magnetotactic bacteria. It is a pale pink to metallic blue-black mineral with a specific gravity of 4.049 and a Mohs hardness of 4 to 4.5. 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. ... The term sulfide (sulphide in British) refers to several types of chemical compounds containing sulfur in its lowest oxidation number of -2. ... In physics, magnetism is a phenomenon by which materials exert an attractive or repulsive force on other materials. ... // Headline text Magnetite is a ferrimagnetic mineral form of iron(II,III) oxide, with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. ... Biomineralisation (or biomineralization) is the process in which living organism produce minerals, often to harden or stiffen existing tissues in living organisms. ... Magnetotactic bacteria are a class of bacteria discovered in the 1970s that are characterised by being able to orient themselves in response to the Earths magnetic field (magnetotaxis). ... Relative density (also known as specific gravity) is a measure of the density of a material. ... Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer. ...
It was first described in 1964 and named for Penn State mineralogist and physical chemist Joseph W. Greig (1895-1977). It has been suggested that University Park, Pennsylvania be merged into this article or section. ...
Greigite is being identified increasingly as an authigenic magnetic mineral in anoxic sediments due to its characteristic magnetic signature [19-21], and, together with hexagonal pyrrhotite, it is used as a paleomagnetic indicator .
Wilkin and Barnes observed that the solid-state reaction of greigite to pyrite requires the outward diffusion of iron, the reduction of ferric iron and the oxidation of sulfide to disulfide .
The reaction-order of the transformation of greigite to pyrite under hydrothermal conditions was not in agreement with that proposed for an oriented aggregation mechanism .
There is no specific data on health dangers or toxicity for this mineral, however you should always treat mineral samples as potentially toxic/dangerous and use sensible precautions when handling them.
Skinner, Brian John, R.C. Erd, & F. Grimaldi (1964), Greigite, the thiospinel of iron, a new mineral: American Mineralogist: 49: 543-555.
Brizzi, G. & Meli, R. (1995): La miniera antimonifera di Pereta con un cenno a quella solfo-cinabrifera di Zolfiere in comune di Scansano (GR).
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