Autunite (hydrated calcium uranyl phosphate), with formula Ca(UO₂)₂(PO₄)₂·10–12H₂O, is a yellow-greenish

fluorescent Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, ...

phosphate In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phosph ...

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

with a

hardness In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard ...

of 2–. Autunite crystallizes in the

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 ...

system and often occurs as tabular square

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...

s, commonly in small crusts or in fan-like masses. Due to the moderate

uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...

content of 48.27% it is

radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consi ...

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 Autun () is a subprefecture of the Saône-et-Loire department in the Bourgogne-Franche-Comté region of central-eastern France. It was founded during the Principate era of the early Roman Empire by Emperor Augustus as Augustodunum to give a Ro ...

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

, which is also autunite's namesake. It occurs as an

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or ...

product of uranium minerals in

granite Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies un ...

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 silici ...

s and

hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...

deposits. Associate minerals include metaautunite,

torbernite Torbernite is a radioactive, hydrated green copper uranyl phosphate mineral, found in granites and other uranium-bearing deposits as a secondary mineral. Its name derives from the Swedish chemist Torbern Bergman (1735–1784), It is also known ...

phosphuranylite Phosphuranylite is a uranyl phosphate mineral with formula KCa(H3O)3(UO2)7(PO4)4O4·8(H2O). It was first described in 1879 by Frederick Augustus Genth, from an occurrence in the Flat Rock pegmatite in Mitchell County, North Carolina Mitchell ...

saleeite Saleeite is a secondary uranium mineral occurring in the oxidized zones of uranium deposits, or as disseminations in carnotite-bearing sandstones. Its chemical formula is Mg(UO2)2(PO4)2·10(H2O). It was discovered in 1932 at Shinkolobwe, Katang ...

uranophane Uranophane ( Ca( U O2)2( SiO3O H)2·5 H2O), also known as uranotile, is a rare calcium uranium silicate hydrate mineral that forms from the oxidation of other uranium-bearing minerals. It has a yellow color and is radioactive. Alice Mary Weeks, a ...

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,

, 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 Parks ...

Spokane Spokane ( ) is the largest city and county seat of Spokane County, Washington, United States. It is in eastern Washington, along the Spokane River, adjacent to the Selkirk Mountains, and west of the Rocky Mountain foothills, south of the Ca ...

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...

(or sometimes referred to as "near Mount Spokane"), in "

vugs A vug, vugh, or vugg ( ) is a small- to medium-sized cavity inside rock. It may be formed through a variety of processes. Most commonly, cracks and fissures opened by tectonic activity ( folding and faulting) are partially filled by quartz, c ...

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 displ ...

, and

shear zones Boudinaged quartz vein (with strain fringe) showing ''Fault (geology)">sinistral shear sense'', Starlight Pit, Fortnum Gold Mine, Western Australia In geology, shear is the response of a rock to deformation usually by compressive stress and f ...

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 ...

, which may have helped lead to the formation of autunite, by providing a source of

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 an

alteration 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 ...

uraninite Uraninite, formerly pitchblende, is a radioactive, uranium-rich mineral and ore with a chemical composition that is largely UO2 but because of oxidation typically contains variable proportions of U3O8. Radioactive decay of the uranium causes ...

and other

bearing minerals. Autunite is also found in

Cornwall Cornwall (; kw, Kernow ) is a Historic counties of England, historic county and Ceremonial counties of England, ceremonial county in South West England. It is recognised as one of the Celtic nations, and is the homeland of the Cornish people ...

Saxony Saxony (german: Sachsen ; Upper Saxon German, Upper Saxon: ''Saggsn''; hsb, Sakska), officially the Free State of Saxony (german: Freistaat Sachsen, links=no ; Upper Saxon: ''Freischdaad Saggsn''; hsb, Swobodny stat Sakska, links=no), is a ...

, and

North North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating direction or geography. Etymology The word ''north ...

and

South Dakota South Dakota (; Sioux: , ) is a U.S. state in the North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Lakota and Dakota Sioux Native American tribes, who comprise a large po ...

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 with

lacquer 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 c ...

to avoid drying of the mineral.

Gallery

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

References

{{Wikisource1911Enc, Autunite Calcium minerals Uranium(VI) minerals Phosphate minerals Orthorhombic minerals Minerals in space group 62 Luminescent minerals Radioactive minerals