AUE1FEE0US GEAVEL. 289 



so that they could be readily worked, but only yielded, on testing, from 

 one-eighth to one-half a cent to the pan in very fine dust gold. 



The gold is derived from the igneous rocks forming Warren Peaks, 

 most of it apparently from the manganese and limonite ledge on the north- 

 east slope, as the largest quantities were found in the ravines heading near 

 that point. The intrusion of the trachyte forming the peaks having dis- 

 turbed the Cretaceous sandstone and the underlying beds, it is probable 

 that the Bear Lodge range was coeval with that of the main range of the 

 Black Hills at the close of the Cretaceous period, and that the gold in the 

 trachyte Avas simultaneously, deposited. In reviewing this small district, 

 which is very interesting scientifically, even if the deposits of gold should 

 not be found of workable richness, it may be stated that the bars are of 

 limited area, and usually shallow deposits of feldspar gravel. The gold is 

 fine, and up to the present time has not been found in remunerative quan- 

 tities. The water supply is small, but probably sufficient for working pur- 

 poses during the spring months. The district is remarkable in the occur- 

 rence of gold without any quartz whatever being associated with it, and in 

 the fact that the gold is derived from feldspar trachyte-porphyry of so 

 recent a geological age. 



SECTION VIII. 



DEPOSITS OF AUEIFEEOUS GEAVEL IN THE FOOTHILLS. 



A belt of gravel deposits, resting usually on the Red Beds near the 

 edge of the plains, extends from Red Canon Creek, in the extreme southern 

 end of the Black Hills, all along the southeastern foothills, across the val- 

 leys of Minnekata, Amphibious, French, Wiwi, Whiske}^ Spring, and Rapid 

 Creeks to Box Elder, where the deposits thin out and disappear. On exam- 

 ination these gravel beds seem to be river deposits, though in places they 

 cap hills 300 feet above the present bed of the nearest stream. Where the 

 divides between the creeks are quite wide, at the edge of the plains, the 

 gravel is seen to be thickest and most extensively deposited near the valleys 

 of the streams, and to thin out toward the crests of the divides. The gravel 

 appears to have been deposited by the water at the point where the power 

 19 b n 



