REPORT OF THE DIRECTOR IQJlJ 205 



more generally it occurs in spots along them, with little or no car- 

 notite in the intervening spaces. As these outcrops are followed 

 into the hillsides, the ore appears to be even more irregular in its 

 distribution than on the surface, and in many or most cases it 

 becomes much scarcer the further it is explored underground, until 

 within i o to 40 or 50 feet from the surface it often mostly or entirely 

 disappears. There are exceptions to this feature, but the gradual 

 and often rapid decrease in quantity and grade of the carnotite ore 

 as it is followed into a hill is generally recognized. This fact sug- 

 gests that the carnotite may have been redissolved in the sandstone 

 and carried to the surface by capillary action in this arid climate, 

 forming rich, superficial efflorescences. 



In many of the carnotite deposits, vanadium minerals occur 

 independently of the vanadium in the carnotite, but this association 

 is not always observed. They occur in sandstone and often give 

 it a dark-gray or blackish color. 



In eastern Colorado several mines near Central City, Gilpin 

 county, have produced limited quantities of pitchblende. Among 

 these are the Kirk, the Wood, the Belcher, the Alps, the German 

 and the Calhoun mines. The pitchblende occurs as a subordinate 

 constituent in the gold-bearing veins of that country. The veins 

 intersect old metamorphic rocks intruded by igneous rocks. The 

 mines of Gilpin county are today producing little if any pitch- 

 blende, and the total production has been small, amounting in all 

 probably to only a few tons. Much more pitchblende, however, 

 was let go to waste in former days when the mines were worked for 

 other ores and the value of uranium was not recognized. 



Production. The United States is today by far the largest pro- 

 ducer of radium and uranium ores in the world, and is also the 

 largest producer of manufactured radium and uranium compounds. 

 Before the war, England, France and Germany, especially Germany, 

 imported large quantities of American ores and extracted the radium 

 in a refined state as its different salts, much of which was returned 

 to the United States for sale. Now, however, American ores are 

 almost entirely treated in the United States, with the exception 

 of a little shipped to England and possibly to France. The Stand- 

 ard Chemical Company of Pittsburgh was a pioneer in .this work 

 and others quickly followed, among them the National Radium 

 Institute of Denver, the Schlesinger Radium Company of Denver, 

 the Chemical Products Company of Denver, the Cummings Chemical 

 Company of Landsdowne, Pa., the Radium Luminous Materials 

 Corporation of New York, and others. 



