Uranium ore support a neutron-mediated chain reaction). Uranium, thorium, and potassium are the main elements contributing to natural terrestrial radioactivity. Uranium has the highest atomic weight of the naturally occurring elements and is approximately 70% denser than lead, but not as dense as tungsten, gold, platinum, iridium, or osmium. It is always found combined with other elements. Along with all elements having atomic weights higher than that of iron, it is only naturally formed in supernova explosions. The primary uranium ore mineral is uraninite (UO) (previously known as pitchblende). A range of other uranium minerals can be found in various deposits. These
Galena, Illinois Galena, Illinois Galena is the largest city in and the county seat of Jo Daviess County, Illinois, with a population of 3,429 at the 2010 census. A section of the city is listed on the National Register of Historic Places as the Galena Historic District. The city is named for the mineral galena, which was mined by Native Americans in the area for over a thousand years. Owing to these deposits, Galena was the site of the first major mineral rush in the United States. By 1828, the population was estimated at 10,000, rivaling the population of Chicago at the