204 NEW YORK STATE MUSEUM 



RADIUM AND URANIUM RESOURCES OF THE UNITED 



STATES 



General statement. The commercially important deposits of 

 ores of radium and uranium in the United States are, so far as yet 

 known, confined to the carnotite regions of southwestern Colorado 

 and southeastern Utah, and the pitchblende deposits of Gilpin 

 county in eastern Colorado. In Connecticut, North Carolina and 

 elsewhere, some little uraninite, pitchblende and other uranium 

 minerals have been found; and near Mauch Chunk in Pennsylvania, 

 small quantities of carnotite 1 have been discovered, but these occur- 

 rences are, so far as known, in quantities too small to be of 

 commercial value. 



Colorado and Utah. The carnotite deposits of southwestern 

 Colorado and southeastern Utah are the most important sources of 

 radium and uranium in the world. In Colorado the largest quanti- 

 ties of ore have come from many mines in Montrose county, 

 especially in Paradox valley, while Mesa, San Miguel, Dolores, Rio 

 Blanco, Routt and other counties have been producers. In south- 

 eastern Utah the ores are carnotite, as in southwestern Colorado, 

 and occur especially in Grand, Emery and San Juan counties, but 

 have not been worked to the same extent as in Colorado. 



The carnotite of Colorado and Utah occurs as an impregnation 

 in sandstones and shaly sandstones, mostly in the McElmo and 

 the La Plata formations, lying at the top of the Jurassic beds and 

 below the Cretaceous sandstones and conglomerates of the region. 

 The deposits seem to have been formed by the precipitation of 

 carnotite from solution along certain strata of these formations, 

 and the material occurs along bedding planes, in fissures and small 

 cavities, in layers or irregular masses from a fraction of an inch to 

 several inches in width, and sometimes as a general impregnation 

 of the' sandstone for several feet in thickness. It seems to be 

 especially abundant in strata impregnated strongly with vegetable 

 or animal matter, and is often in unusual quantities in lignitized 

 or petrified trunks of trees. This phenomenon suggests the influence 

 of organic matter in precipitating and segregating the carnotite. 



The rocks carrying the carnotite lie horizontally or dip at low 

 angles in most parts of the Colorado region; in Utah they lie often 

 in the same way, but occasionally dip at steep angles. Where they 

 appear on the surface, the carnotite sometimes impregnates certain 

 strata for several hundred feet or more along the outcrops, but 



1 Edgar T. Wherry, A New Occurrence of Carnotite, Amer. Jour. Sci., 33:574- 

 80. 1912. 



