THE RARE METAL* 279 



radioactive, and uranium itself may be the progenitor of its more 

 highly active companion, radium. Tin- mineral is remarkable 

 in that it pi-incuts the only instance in which nitrogen has been 

 found belonging to the original crust of the earth. Uranniobite 

 is t hr crystallized variety of uraninite in which the element nitro- 

 gen occurs in its maximum percentage, 2.6 per cent. 



Broggerite, UO 2 , U0 3 , ThO 2 , occurs in octahedral crystals. 



Cleveite, UO 2 ,UO 3 ,Th0 2 , Y 2 3 , the trioxide, U0 3 , is present in 

 larger percentage in cleveite than in the preceding minerals. 

 It crystallizes in hexahedrons, often modified by other funda- 

 mental isometric forms. 



Nivenite, UO 2 , U0 8 , Th0 2 , Y 2 O 3 , occurs massive, velvet-black in 

 color and is more soluble than the other varieties of uraninite. 



Pitchblende, UO 2 , UO 3 , is massive uraninite. ThO 2 and the 

 rare earths are absent, while nitrogen is sparingly present, if 

 represented at all. 



Coracite is an alteration product of uraninite in its transition to 

 gummite. 



Gummite, (PbCa)U 3 , SiOi 2 , 6H 2 O, is an alteration product of 

 uraninite which occurs in rounded or flattened pieces, closely 

 resembling gum. 



Carnotite is cited by H. Ries as occurring in Montrose County, 

 Colo., and also in Utah. Carnotite is a vanadate of uranium and 

 potassium which occurs in canary-yellow impregnations in sand- 

 stones in western Colorado and eastern Utah. It is second in 

 importance of the uranium-bearing minerals. 



There are several well known hydrous arsenates and phosphates 

 of uranium and the alkaline earth metals, but they are not of 

 commercial significance. 



Origin of the Ores. Most of the minerals bearing uranium are 

 of secondary origin. The columbates and tantalates of iron 

 containing uranium are primary constituents of pegmatites. 



Character of Ore Bodies. Uraninite is sometimes obtained 

 from metalliferous veins, but more often it is found in association 

 with acid intrusives, granites and pegmatites. In Colorado it is 

 obtained from a schistose granite which in places gives way to 

 porphyry. Uranium is chemically unlike vanadium, with which 

 it is associated in one of its most important ores; viz., carnotite. 

 Uranium has been found in coal; in an anthracitic mineral in a 

 pegmatite vein in Canada; in anthracitic bitumen from Sweden; 

 and in the ashes of seaweeds. Carnotite occurs as impregnation 



