U-rā'ni-ŭm, n.

n. [N. Lat., from Gr. οὐρανός, heaven, in mythology, the son of Erebos and Gaia, and father of Saturn; or from Uranus, the planet.] (Min.) A metal discovered in 1789, by Klaproth, in the mineral called pitchblende, in which it exists as an oxide, with oxide of iron, and some lead, sulphur, arsenic, cobalt, and zinc. It occurs also in uranite and uran-ocher, and a few other minerals. Uranium is of a reddish-brown color, has a metallic luster, and is commonly obtained in a crystalline form. It suffers no change from exposure to the air at common temperatures, but when heated in open vessels, it absorbs oxygen, and is converted into a protoxide. Dana.