Radium seventh of a gram of radium. One kilogram of the Earth's crust contains about 900 picograms of radium, and one liter of sea water contains about 89 femtograms of radium. Radium was discovered by Marie Sklodowska-Curie and her husband Pierre Curie on 21 December 1898, in a uraninite (pitchblende) sample. While studying the mineral earlier, the Curies removed uranium from it and found that the remaining material was still radioactive. They separated out an element similar to bismuth from pitchblende in July 1898, that turned out to be polonium. They then separated out a radioactive mixture consisting mostly of two
Radium Hill named the uranium-bearing mineral davidite after geologist and Antarctic explorer, Sir Edgeworth David. The mine was initially called "Smith's Carnotite Mine" (a similar uranium-bearing mineral) and in September 1906 Mawson proposed the name "Radium Hill". Smith worked the mine for the next two years before allowing the lease to lapse. Adjoining leases stretched for along the lode, with one being half-owned by Mawson. The Radium Hill Company took over the lease in 1908 and more shafts were sunk. Ore concentrate was transferred to refineries in New South Wales and Victoria. Radium had reached a price of ₤13,000 per gram in