W. P. Headden — T antedate from So. Dakota. 293 



Art. XXVIII. — A Tantalate and Some Columbites from 

 Custer County, South Dakota; by William P. 

 Headden. 



The minerals presented in these notes are from Custer 

 Co., South Dakota, with the exception of one columbite 

 which was found near Harney City, Pennington Co. They 

 were all collected by Mr. George B. Grant with the excep- 

 tion of the tapiolite which was collected by the writer 

 many years ago. 



The columbites have the habit and physical properties 

 of this mineral as it occurs in other districts of the Black 

 Hills, but there were very pronounced differences among 

 them in specific gravity, color, and habit. They all 

 showed the tabular form with striations. The fracture 

 was uneven, inclining to granular; the color was brown 

 or grayish black, with slightly shining sub-metallic luster 

 but wholly free from iridescence. 



The tantalate differed from these columbites in all of its 

 physical properties. It is a pure black in color, with 

 shining metallic to adamantine luster and a strong irides- 

 cence ; it is brittle and harder than the columbites and has 

 a higher specific gravity. 



The fragments received were small, irregular in form, 

 sharp angled, and showed no satisfactory cleavage sur- 

 faces. It is doubtful whether they actually show any 

 cleavage surfaces at all. The fragments were freshly 

 broken and clean, but there was a white, triclinic feldspar, 

 apparently microcline, adhering to some of them. These 

 fragments appear to have been originally parts of masses 

 that had been cracked and the surfaces thus produced 

 coated with a thin film of silica. Some of them contain 

 small pieces of quartz, but only occasionally a flake of mica. 

 The tantalate is all from one locality, the Old Mike Mica 

 mine in the Minnehaha Gulch, 6% miles north of Custer 

 City, Custer Co., South Dakota. The columbite is from 

 three localities, two of them in Custer Co. ; these are the 

 Old Mike Mica mine and Tin Mountain on Warren's Gulch ; 

 the remaining one is from Harney City, in Pennington Co. 

 This last locality is not far from the Etta mine in the 

 Harney Peak district which formerly furnished many fine 

 specimens of columbite, some of which have been 

 described in earlier numbers of this Journal. I never 



Am. Jour. Sci.— Fifth Series, Vol. Ill, No. 16. — April, 1922. 

 21 



