Blake — Columbite of 'the Black Hills, South Dakota. 403 





l. 



2. 



Mean. 



Ratio. 





Calculated. 



Bi... 



76-94 



78-14 



77-54 



•371 



10 



77-08 



S.__. 



14-15 



13-96 



14-06 



•440 



12 



14-18 



Se.... 



8-80 



not det. 



8-80 



•111 



3 



8-74 



99-89 100-40 100-00 



This would prove the mineral to be a seleniferous bismuthinite 

 of the composition 4Bi 2 S 3 -J-Bi 2 Se 3 . A piece which I received 

 about four years ago from Prof. Carlos F. de Landero of 

 Guadalajara, Mex., more compact, but with slender crystals, 

 imbedded in indurated clay, looks as if it had come from the 

 same mass which furnished Messrs. Geo. L. English & Co.'s 

 specimen. 



B. Guanajuatite or Frenzelite. — The results under " A " 

 suggested repeating the analysis of Guanajuatite with a speci- 

 men which came from an old German collection, purchased 

 about ten years ago. It is compact, granular, indistinctly 

 fibrous and of a light gray color. Spec. grav. = 6*977. The 

 results of the analysis are as follows : 







Ratio. 





Calculated. 



Frenzel found. 



Bi.. 



.. 68-86 



•330 



6 



68-74 



Bi _.. 67-38 



S — 



_. 4-68 



•146 



3 



5-27 



S 6-60 



S -. 



.. 25-50 



•320 



6 



25-99 



Se 24-13 



99-04 100-00 



Corresponding to : Bi 2 S 3 -)-2Bi 2 Se 3 , analogous to the usual vari- 

 ety of tetradymite. The percentage of sulphur, in FrenzePs 

 analysis, seems to be too high ; as it is, the analysis would not 

 lead to a rational formula, but the results are close enough to 

 admit of a comparison with mine and suggest that the same 

 mineral has been analyzed by both of us, and that the exist- 

 ence of the species cannot be questioned. 



Chemical Laboratory, No. Ill S. 10th St., Philadelphia, March 23d, 1891. 



Art. XLYII. — Columbite of the Black Hills, South Dakota / 

 by Wm. P. Blake. 



The publication of the paper on the columbite and tantalite 

 of the Black Hills, of South Dakota, by Mr. W. P. Headden* 

 is timely and important, particularly in giving for the first 

 time a series of careful analyses of the mineral from the Etta 

 Mine and from the Bob Ingersoll Claim, in comparison with 



* This Journal, xli, 89, 1891. 



