Cleveite is a radioactive mineral containing uranium and found in Norway. It is an impure form of uraninite, and has the composition UO₂·UO₃·PO·ThO₂ with about 10% of the uranium substituted by rare earth elements. It was named after Swedish chemist Per Teodor Cleve. Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles. ... Minerals are natural compounds formed through geological processes. ... General Name, Symbol, Number Uranium, U, 92 Chemical series Actinides Period, Block 7, f Density, Hardness 19050 kg/m3, 6 Appearance silvery-white metal Atomic properties Atomic weight 238. ... Uraninite is a uranium-rich mineral with a composition that is largely UO2 (uranium oxide), but which also contains UO3 and oxides of lead, thorium, and rare earths. ... A rare earth is an oxide of a rare earth element. ... Per Teodor Cleve (Stockholm February 10, 1840 - Uppsala June 18, 1905) was a Swedish chemist and geologist. ...

Cleveite was the first known terrestrial source of helium, which is created by the alpha radiation of the uranium and then lies trapped (occluded) within the mineral. The first sample of helium was obtained by William Ramsay in 1895 when he treated a sample of the mineral with acid. Cleve and Abraham Langlet succeeded in isolating helium from cleveite at about the same time. General Name, Symbol, Number helium, He, 2 Chemical series noble gases Group, Period, Block 18, 1, p Appearance colorless Atomic mass 4. ... An alpha particle is deflected by a magnetic field Alpha particles or alpha rays are a form of particle radiation which are highly ionizing and have low penetration. ... William Ramsay. ... 1895 was a common year starting on Tuesday (see link for calendar). ... An acid (often represented by the generic formula AH) is typically a water-soluble, sour-tasting chemical compound. ... Nils Abraham Langlet (July 9, 1868 - March 30, 1936; known by his second given name) was a Swedish chemist. ...

Yttrogummite is a variant of cleveite also found in Norway.