Group 3 element it from pitchblende residues left by Marie and Pierre Curie after they had extracted radium. In 1899, Debierne described the substance as similar to titanium and (in 1900) as similar to thorium. Friedrich Oskar Giesel independently discovered actinium in 1902 as a substance being similar to lanthanum and called it "emanium" in 1904. After a comparison of the substances half-lives determined by Debierne, Hariett Brooks in 1904, and Otto Hahn and Otto Sackur in 1905, Debierne's chosen name for the new element was retained because it had seniority, despite the contradicting chemical properties he claimed for the element at different
Uranium mining in Colorado oxide. The mine is owned by General Atomics subsidiary the Cotter Corporation, which estimates that there are an additional 16 million pounds (7300 metric tons) of uranium oxide resource remaining in the mine. The Copper King mine, in Larimer County about 25 miles northwest of Fort Collins and 5 miles northeast of Red Feather Lakes contained a skarn deposit that was worked unsuccessfully for zinc in 1920 and 1936. Prospectors found uranium at the abandoned mine in 1949, and it was worked for uranium from 1951 until 1953. The uranium occurs as pitchblende in a hydrothermal vein deposit in Precambrian