404 Blake — Columbite of the Black Hills, /South Dakota. 



the composition of the species from other localities. It is also 

 agreeable to find that my original determination as columbite 

 of the mineral from both the Etta and the Ingersoll was 

 correct.* 



The specimens collected in 1884 have been carefully pre- 

 served with the intention of preparing a full description for 

 publication so soon as the chemical investigation could be com- 

 pleted. As Mr. Headden's numerous analyses supply this 

 want, it is now necessary only to present a few further notes 

 and the results of a crystallographic study of the specimens, 

 made at my request by Prof. S. L. Penfield, of the Sheffield 

 Scientific School, and reported to me in April, 1890. 



In breaking up the huge mass of columbite at the Ingersoll 

 the only good crystalline terminations were those broken out 

 from the quartz matrix. The mass when discovered by me did 

 not show any crystallization which could have been used for 

 the determination of its form. The exposed portions were 

 rounded and weather worn. The blast which was intended to 

 throw it out whole, if possible, disclosed the fact that it was 

 made up largely of a series of broad plates interleaved in part 

 by a translucent quartz. These plates are crystals flattened 

 parallel to the macropinacoid a, 100, i-l ; some of them with 

 bright crystal faces on the edges. The forms which were 

 identified are as follows : 



&, 010, %-% 

 m, 110, I 



z, 530, i-% 

 cZ, 730, i-l 



Jc, 103, H 



/, 102, \-l 



o, 111, 1 

 u, 133, 1-3 



TV, 121, 2-2 

 n, 163, 2-6 



Fig. 1 represents the ordinary habit of the crystals while 

 fig. 2 represents a more highly modified one which was 

 observed. One small crystal had bright faces and gave on 



the goniometer fair reflections of the signal. Some of the 

 principal measurements for the identification of the faces 

 are given below, and for comparison the calculated angles 

 obtained from the axial relation established by E. S. Dana,f 

 a:b: <b=0'8285 : 1 : 0*88976 



* This Journal, xxviii, 340, 1884. f Zeitschr. Kryst., xii, p. 266, 1886. 



