Period 7 element elements of the 7th period. Francium is a chemical element with symbol Fr and atomic number 87. It was formerly known as eka-caesium and actinium K. It is one of the two least electronegative elements, the other being caesium. Francium is a highly radioactive metal that decays into astatine, radium, and radon. As an alkali metal, it has one valence electron. Francium was discovered by Marguerite Perey in France (from which the element takes its name) in 1939. It was the last element discovered in nature, rather than by synthesis. Outside the laboratory, francium is extremely rare, with trace amounts
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