Clarkeite is a

uranium oxide Uranium oxide is an oxide of the element uranium. The metal uranium forms several oxides: * Uranium dioxide or uranium(IV) oxide (UO2, the mineral uraninite or pitchblende) * Diuranium pentoxide or uranium(V) oxide (U2O5) * Uranium trioxide o ...

mineral with the chemical formula or . Its color varies from dark brown to reddish orange. Clarkeite forms by

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 a ...

and replacement of

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 ...

late during pegmatite crystallization. Although uraninite-bearing

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 under ...

pegmatites are common, clarkeite is rare and occurs intimately intergrown with other

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 ...

minerals. It is known from only two localities; the Spruce Pine pegmatite district in western

North Carolina North Carolina () is a state in the Southeastern region of the United States. The state is the 28th largest and 9th-most populous of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, Georgia and ...

, US, and Rajputana, in the

Ajmer Ajmer is one of the major and oldest cities in the Indian state of Rajasthan and the centre of the eponymous Ajmer District. It is located at the centre of Rajasthan. It is also known as heart of Rajasthan. The city was established as "' ...

district,

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

. Clarkeite is the only known naturally occurring high-temperature uranate. The general formula for ideal clarkeite is . It was named for Frank Wigglesworth Clarke (1847–1931), American mineral chemist, and former chief chemist of the

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

References

Clarkeite: New chemical and structural dataWebMineral
Uranium minerals Sodium minerals Hydroxide minerals Trigonal minerals Minerals in space group 166 {{oxide-mineral-stub

See also

References