Uranium is named for the planet Uranus and was isolated in 1841. Uranium occurs in numerous minerals such as pitchblende, uraninite, carnotite, autunite, uranophane, davidite, and tobernite. It is also found in phosphate rock, lignite and monazite sands from which it can be commercially recovered. Uranium can be prepared by reduciing uranium halides with alkali or alkaline earth metals or by reducing uranium oxides by calcium, aluminum, or carbon at high temperatures. Uranium is a heavy, silvery-white metal which is malleable, ductile and slightly paramagnetic. Uranium is of great importance as a nuclear fuel. Depleted uranium (U235 lowered to about 0.2%) has found use in inertial guidance devices, gyro compasses, counterweights for aircraft control surfaces, ballast for missile reentry vehicles and as a shielding material. Uranium and its compounds are highly toxic, both from a chemical and radiological standpoint.