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Autunite (hydrated calcium uranyl phosphate), with formula Ca(UO2)2(PO4)2·10–12H2O, is a yellow-greenish fluorescent phosphate mineral with a hardness of 2–. Autunite crystallizes in the
Researchers found autunite inside the Daybreak Mine on
File:Autunite UV(AB) France.jpg, Autunite under UV light
File:Autunite sous UV (France).jpg, More crystals under UV light
File:Autunite09.jpg, Scaly crystals of autunite
File:Autunite (France).JPG, Autunite from France
File:Autunite-141164.jpg, Close-up of an autunite crystal
orthorhombic
In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a r ...
system and often occurs as tabular square crystals, commonly in small crusts or in fan-like masses. Due to the moderate uranium content of 48.27% it is radioactive and also used as uranium ore. Autunite fluoresces bright green to lime green under UV light. The mineral is also called calco-uranite, but this name is rarely used and effectively outdated.
Autunite was discovered in 1852 near Autun, France, which is also autunite's namesake. It occurs as an oxidation product of uranium minerals in granite pegmatite
A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic com ...
s and hydrothermal deposits. Associate minerals include metaautunite, torbernite, phosphuranylite, saleeite, uranophane and sabugalite.
Etymology
Autunite was named after the town of Autun, France, where the mineral was initially found. The mineral was named by Henry J. Brooke and William H. Miller in 1854. The archaic name "calco-uranite" pairs with the similarly composed mineral, torbernite, which was named "cupro-uranite". Both minerals are named due to their uranium content, with autunite's name referring to its calcium (''calco''), and torbernite's copper (''cupro'') quantity.Locations and mining
Mount Kit Carson, Washington
Researchers found autunite inside the Daybreak Mine on Mount Kit Carson
Mount Kit Carson is a mountain in the northwest United States, located in Spokane County, Washington, northeast of Spokane, with a summit elevation of above sea level. It is in Mount Spokane State Park, the largest of Washington's State Park ...
, Spokane, Washington (or sometimes referred to as "near Mount Spokane
Mount Spokane levation €”previously known as Mount Baldy until 1912 due to its pronounced bald spot—is a mountain in the northwest United States, located northeast of Spokane, Washington. Its summit is the highest point in Spokane County, an ...
"), in " vugs, fractures
Fracture is the separation of an object or material into two or more pieces under the action of stress. The fracture of a solid usually occurs due to the development of certain displacement discontinuity surfaces within the solid. If a displa ...
, and shear zones in granitic rock". These areas showed signs of another phosphate, apatite
Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of OH−, F− and Cl− ions, respectively, in the crystal. The formula of the admixture of the three most common e ...
, which may have helped lead to the formation of autunite, by providing a source of phosphate and lime. The formation may have occurred with the interaction of uranium leached from a separate deposit.
90,000 lbs of U3O8 were produced from nine properties, although most of the ore came from the Daybreak Mine.
Other locations
One of the other locations of autunite includes Autun, France, the type locality and namesake of the mineral. The mineral was formed there as analteration
Alteration(s) may refer to:
* Alteration (music), the use of a neighboring pitch in the chromatic scale in place of its diatonic neighbor.
** Alteration, in the mensural notation used by renaissance music, the lengthening of a breve, semibreve or ...
of uraninite and other uranium bearing minerals. Autunite is also found in Cornwall, Saxony, and North and South Dakota.
Meta-autunite
If the mineral dries out, it can lose its water content and convert to meta-autunite-I, which can turn into meta-autunite-II after heating. These two subsequent minerals are very rare in nature. For scientific studies it is recommended to store the mineral in a sealed container to minimize the water loss. Museums are known to have covered the mineral withlacquer
Lacquer is a type of hard and usually shiny coating or finish applied to materials such as wood or metal. It is most often made from resin extracted from trees and waxes and has been in use since antiquity.
Asian lacquerware, which may be ca ...
to avoid drying of the mineral.
Gallery
References