THE RARE METALS 281 



trioxidc is used to paint porcelain red, and is also used in calico 

 printing. 



Columbium 



Properties. Columbium, symbol Cb, is a rare acid-forming 

 element, closely allied to tantalum. Its melting point is 1950 C, 

 its specific gravity is 7.2, and its atomic weight is 93.5. 



Ores of the Metal. Columbite, FeO, Cb 2 O5, is a columbate of 

 iron. It crystallizes in the orthorhombic system. Its color is 

 brownish-black to black. 



Manganocolumbite, MnO, Cb 2 5 , is a columbate of manganese, 

 in which manganese has displaced the iron of normal columbite. 

 Iron may be present in considerable quantity. 



Samarskite, R" 2 , R'" 3 , (CbTa) 6 O 21 , where R" = Fe, Ca, UO 2 

 and R'" = Ce,Y. The mineral is a rare columbate and tantalate 

 of iron, calcium, uranium, and the rare earth metals. 



Euxenite is a columbate and titanate of the rare earths. It is an 

 altered samarskite. 



Pyrochlore is a metacolumbate of calcium and cerium. 



Fergusonite is a metacolumbate of Y, Er, Ce and U. 



Sipylite is a columbate of erbium. 



. There are several other rare minerals of which columbium is a 

 constituent. 



Character of the Ore Bodies. Columbite is a primary mineral, 

 found in the acid intrusives, granites and pegmatites. In these 

 veins single masses of columbite have been obtained weighing 

 more than 2000 pounds. 



Geographical Distribution. Columbite is found sparingly in 

 the Appalachian belt in North Carolina, Virginia, Pennsylvania, 

 New York, New Hampshire, Connecticut and Maine. In Maine, 

 columbite is associated with cassiterite. In New Hampshire, 

 at Acworth, it is associated with beryl; in New York, at Green- 

 field, it is associated with chrysoberyl. The Appalachian belt is 

 scarcely of commercial significance. Columbite occurs in Colo- 

 rado near Canon City, and at the Etta mine in the Black Hills, 

 South Dakota. The largest masses found in America occurred in 

 the Etta mine in association with cassiterite. 



Uses. The interest attached to columbium at present is due 

 to the incandescent lamp industry. There is little if any pro- 

 duction of columbite other than for the tantalum present, and 

 for museum and laboratory materials. 



