Minerals containing Columbium. 417 



subjected to analysis.* This variety, or rather, this new 

 species, I distinguish by the name ferrotantalite ; because 

 it consists almost wholly of columbic acid combined with 

 protoxide of iron. 



Colour black. 



In irregular masses, with some indications of crystalline 

 faces ; though it is impossible to make out the shape of the 

 crystal. 



Lustre metallic, and, in general, greater than that of 

 common tantalite. Internal lustre often less, owing to 

 large rents in the mineral, the surfaces of which exhibit a 

 rainbow tarnish. 



Fracture uneven. Hard enough to scratch glass. Specific 

 gravity 7*655. 



Powder dark reddish brown, becoming lighter the more 

 finely it is pounded. 



Not acted on by acids. 



Before the blow-pipe, ^erse, not altered. With borax, 

 when in solid pieces, it dissolves very slowly, or not at all. 

 In fine powder, it dissolves very slowly. The glass has a 

 green colour, in which white particles float : and it does 

 not become milky by flaming. In bi-phosphate of soda, it 

 dissolves much more easily, and the glass has the same 

 colour as when common tantalite is employed. The addition 

 of saltpetre indicates a small quantity of manganese. 



With carbonate of soda it does not dissolve. But when 

 it is heated with a mixture of carbonate of soda and borax 

 on charcoal, and exposed to a good reducing heat grains of 

 tin are obtained. 



Being subjected to analysis by Berzelius, he obtained, 

 Columbic acid, .... 85*85 

 Protoxide of iron, . . . 12*97 

 Protoxide of manganese, . 1*61 



Oxide of tin, 0*80 



Lime, 0*56 



Silica, 0*72 



102*51t 



* Afhandlingar, vi. 237. 



t Afhandlingar, vi. 243. The excess is probably owing to over-rating the 

 quantity of columbic acid in the mineral. Had the amount been 83-43, the atoms 

 of acid and bases would have been the s;une. Now, the difference between 8/)'85 

 and 83*43 is 2*42, which is very nearly the amount of the excess. 



VOL. IV. 2 E 



