Autunite


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autunite

[ō′tə‚nīt]
(mineralogy)
Ca(UO2)2(PO4)2·10H2O A common fluorescent mineral that occurs as yellow tetragonal plates in uranium deposits; minor ore of uranium.

Autunite

 

(named after the city of Autun, in Saône-et-Loire Department France), a mineral of the uranite group. Autunite has a chemical formula of Ca(UO2)2[PO4]2·8H2O; it contains 62.7 percent UO3. The mineral crystallizes in the tetragonal system, primarily forming thin tabular, micaceous, or tetragonal crystals. Scaly aggregates also occur. Autunite varies in color from lemon yellow to sulfur yellow; sometimes it is green. The mineral has a pearly luster and is highly radioactive. Its hardness on Mohs’ scale is 2–2.5, and its density is 3,050–3,190 kg/m3. Autunite is formed as a result of surface changes in various uranium minerals (particularly uraninite), in hydrothermal veins, and in pegmatites. It is an ore of uranium.

References in periodicals archive ?
The primary uranium minerals are uraninite and coffinite but numerous secondary uranium minerals have been formed as a result of the weathering processes: yellow gummites, autunite, metaautunite, torbernite, saleeite, uranotyle, ianthinite and uranopilite (Arribas, 1975).
The strongly sheared samples (such as sample 139, Table 2) have geochemical characteristics comparable to the mineralized zones containing chalcopyrite, pyrite, sphalerite, and autunite from the Millet Brook deposit (Chatterjee and Strong 1984), although the alteration intensity and elemental enrichment are much less pronounced in the drill core samples (Table 1).
Autunite has been reported as a very minor supergene mineral produced by weathering of alteration products of early-stage veins at the Globe Hill mine, and associated with other secondary uranium minerals in Tertiary volcanics (Thompson et al.
Allan's Chilean proustite, Tsumeb dioptase, Tur kish kammererite, Mexican acanthite, Congo cuprite; Ralph's Swiss anatase, Brazilian autunite, North Carolina hiddenite; both men's Montana veszelyites .
Big autunite specimens from the Daybreak mine near Spokane, Washington, are notorious for dehydrating and exfoliating or splitting over time.
Autunite occurs rarely at Sapucaia, as small crystals perched on (or enclosed in) variscite, and as fissure coatings in albite near johnsomervilleite crystal groups.
Common examples include autunite and some fluorite, especially the purple/green specimens from Durham, England, which fluoresce blue.
Autunite is erroneously quoted in early internal reports; but in fact there is no radioactivity at all in the primary ore.
Agnes, liroconite crystals on matrix from Huel Gorland, beautiful chalcophyllite groups, botryoidal malachite from Wheal Unity, gold nuggets, superb cubic and octahedral cuprite crystals on matrix, lustrous jet-black sphalerite crystals, blue-tarnished chalcopyrite crystals on quartz, torbernite and autunite crystals, phenakite crystals from St.