Polonium the Curies while they were investigating the cause of pitchblende radioactivity. Pitchblende, after removal of the radioactive elements uranium and thorium, was more radioactive than the uranium and thorium combined. This spurred the Curies to search for additional radioactive elements. They first separated out polonium from pitchblende in July 1898, and five months later, also isolated radium. German scientist Willy Marckwald successfully isolated 3 milligrams of polonium in 1902, though at the time he believed it was a new element, which he dubbed "radio-tellurium", and it was not until 1905 that it was demonstrated to be the same as polonium.
Uranium mining in Colorado is associated with faulting-induced fractures in the sandstone. Horizon Nevada Uranium Inc. has announced plans for exploration drilling in 2008 for uranium in the South Park Ranch area of southeast Park County. The Cochetopa mining district is about 20 miles southeast of Gunnison in northwest Saguache and southern Gunnison County. Uranium was discovered in outcrops of the Morrison Formation (Jurassic). Mineralization occurs in silicified (chalcedony and quartz) veins cutting the Morrison Formation and the subjacent Precambrian schist. The veins contain pitchblende, autunite and uranophane, with accessory marcasite and barite. Extraction started in 1954, by underground mining. Uranium was discovered near