526 MINERALOGY 



down of uranium ; pitchblende is therefore radioactive, and is at 

 present the source of radium. 



Crystals of uraninite occur in the granites and pegmatites of 

 Moss and Arendal, Norway ; Cornwall, England ; and in the feld- 

 spar quarries of Middletown, Connecticut. The massive mineral 

 is associated with ore veins at Joachimsthal and Schneeberg. In 

 the United States it is found in Gilpin County, Colorado ; in the 

 Black Hills, South Dakota, and in Llano County, Texas. 



It is the present source of radium and uranium. 



Uranium compounds are used in the laboratory in the determi- 

 nation of phosphorus and zinc ; in photography ; in pottery glazes ; 

 for -coloring glass ; in the manufacture of special steels for use in 

 gun barrels, and as a pigment. 



Gummite is an alteration product of uraninite, of a light reddish 

 yellow or yellowish brown color, containing considerable water. 

 It is associated with the pitchblende of Flat Rock, Mitchell County, 

 North Carolina. Some of the rounded masses of orange-red color 

 still contain a nucleus of unaltered uraninite. 



