Many of the mines of the Goodsprings District exhibit anomolous radioactivity attributable to uranium and its decay products. Most commonly the radioactivity is localized by limonite, hydrozincite, ferruginous chert and chrysocolla. Secondary uranium minerals are rare and no primary uranium minerals were identified. The radioactivity from those materials that are free from visible uranium minerals is attributed to uranium adsorbed from solution by colloidal substances during the oxidation of pitchblende-bearing primary sulfide ore bodies. Laboratory studies show that uranyl carbonate, uranyl hydroxide and uranyl ions are adsorbed by colloidal hydrous ferric oxide or basic zinc carbonate. Upon crystallization of the adsorbent, the uranium is either returned to solution or forms discrete uranium minerals within the former adsorbent.