THE NONMETALLIO MINKKALS. 



353 



CiiAs. F. Mabery, OtisT.Flooz. C'lay, liricky, rottery, etr. 



Thirteenth Report of the California State Mineralogi.st, ISIXI, p. lilL'. 

 Thomas C. Hopkins. Clays and Clay Indnstries of Pennsylvania. 



Appendix to the Animal Report of the Pennsylvania State C^oUege for hsi)7. 

 J. Nelson Nevius. Kaijlin in Vermont. 



Engineering and Mining Jonrnal, LXIV, 1897, j). 189. 

 Heinkicii Ries. The Clays and Clay-Working Industry of Colorado. 



Transactions of the American Institute of Mining Engineers, XXVII, 1897, 

 p. 336. 

 H. A. Wheeler. Clay Deposits. 



Missouri (xeological Survey, XI. 

 W. W. Clendennin. Clays of Louisiana. 



Engineering and Mining Journal, LXVI, 1898, p. 456. 

 M. H. Crump. The Clays and Building Stones of Kentucky. 



Engineering and INIining Journal, LXVI, 1898, p. 190. 

 W. C. Knight. Bentonite. [A New Clay.] 



Engineering and Mining Journal, LXVI, 1898, p. 491. 



The Building Stones and Clays of Wyoming. 



Engineering and Mining Journal, LXVI, 1898, p. 546. 

 Heinrich Ries. Physical Tests of New York Shales. 

 School of Mines Quarterly, XIX, 1898, p. 192. 



The Ultimate and the Rational Analysis of Clays and Their Relative Advantages. 



Transactions of the American Institute of Mining Engineers, XXVIII, 1898, 

 p. 160. 

 Eugene A. Smith. The Clay Resources of Alaljama and the Industries Dependent 

 upon Them. 



Engineering and Mining Journal, LXVI, 1898, p. 369. 

 J. E. Todd. The Clay and Stone Resources of South Dakota. 

 Engineering and Mining Journal, LXVI, 1898, p. 371. 



VII. NIOBATES AND TANTALATES. 



1. COLUMBITE AND TANTALITE. 



These are columl^ates and tantalates of iron and manganese, colum- 

 bite representing- the nearly pure cphunbate and tantalitc the nearly 

 pure tantalate. Both are likely to carry varying quantities of iron 

 and manganese. The analyses given below will serve to show the 

 varying composition, No. I being columbito from Greenland, No. II 

 from Haddam, Connecticut, and Nos. Ill and IV from the Black Hills 

 of South Dakota: 



Constituents. 



Columbium pentoxide . 

 Tantalium pentoxide . , 



Iron protoxide 



Manganese protoxide . 



77.97 



17.33 

 3.28 



II. 



51.58 



28.55 



13.54 



4.55 



III. 



54.09 

 18.20 

 11.21 



7.07 



29. 78 



53.28 



6.11 



10. 40 



With traces of tin, wolfram, lime, magnesia, etc. 



The mineral is of an iron black, grayish or brownish color, opaque, 

 often with a bluish iridescence, dark red to black streak, specitic 

 gravity varying from 5.3 to 7.3 and hardness of 6. Insoluble in acids. 

 NAT MUS 99 23 



