Scandium metal is a silvery-white solid that, when exposed to air, takes on a little pink or yellow hue. It has a melting point of 1,538 degrees Celsius (2,800 degrees Fahrenheit) and a boiling temperature of around 2,700 degrees Celsius (4,900 degF). It has a density of 2.99 g/cubic centimeter. Scandium compounds are widely used in alloys because of their unique combination of properties: high strength, low weight, good corrosion resistance, and high elasticity. In chemistry, scandium forms many oxides, including scandium oxide, Sc2O3, which is an insulator. Other common oxidation states include +3, +4, and 0. Scandium compounds are mostly gray or white, with some exceptions such as black scandium tetroxide, Sc(OC2H5)4. Scandium is a rare element in the earth's crust. It occurs mainly in association with iron ore in concentrations up to 0.5 percent. Some other important sources include titanium dioxide pigment, zinc dust, and yttrium minerals. Mining activity can have a significant impact on the environment through soil and water contamination. Production levels have increased significantly since its discovery in 1937, but mining still requires extensive use of energy. Scandium was first discovered in 1937 by American scientists who were looking for new materials for space travel at the University of California, Berkeley.