Radium bromide Institute had four grams of radium total, which at the time was more than half the world supply. Countries all over the world set out to make as much radium as possible, a time consuming and expensive task. It was reported in "Science" magazine in 1919 that the United States had produced approximately 55 grams of radium since 1913, which was also more than half the radium produced in the world at the time. A principal source for radium is pitchblende, which holds a total of 257 mg of radium per ton of UO. Obviously with so little product recovered
Radium closely resemble its lighter congener barium. Pure radium is a volatile silvery-white metal, although its lighter congeners calcium, strontium, and barium have a slight yellow tint. Its color rapidly vanishes in air, yielding a black layer of radium nitride (RaN). Its melting point is either or and its boiling point is . Both of these values are slightly lower than those of barium, confirming periodic trends down the group 2 elements. Like barium and the alkali metals, radium crystallizes in the body-centered cubic structure at standard temperature and pressure: the radium–radium bond distance is 514.8 picometers. Radium has a density