236 GEOLOGY OF THE BLACK HILLS. 



ting deep into the schists and slates. In these ravines float quartz was 

 found, showing, on breaking, visible particles of gold, but the quartz was 

 not traced to the ledge from which it had been originally derived. 



Minnekata or "Hot Water" Creek, so named by the Indians from the 

 warmth of the water, which has a temperature of 74° Fahr., although rising 

 in large warm springs in the Carboniferous limestone, has a deep deposit of 

 quartz-gravel on its east bank, about two miles below its source. This 

 gravel is derived from the wash from the Hills, and is composed of bowlders 

 of rocks and quartz cemented by sand and lime to a loosely cohering con- 

 glomerate, forming a bluff on the bank of the stream. Similar deposits are 

 to be seen at intervals among the foothills at the edge of the plains all 

 along the eastern slope from this stream as far north as the Box Elder. 



On Red Canon Creek several tests were made of the gravel deposits, 

 but nothing of value found This stream is on the extreme western edge 

 of the gold-fields, and rises partly in the limestone, contains but little water, 

 and drains but a limited area of the schistose rocks. 



The gravel deposits elevated above the present level of French Creek 

 showed often a local concentration of gold on the outer edge of the bed- 

 rock from the repeated washing away of the gravel by floods or heavy 

 rains, leaving the gold contained in it behind. Though giving a very 

 encouraging prospect at first, on driving an open cut a few yards into the 

 bar where the gravel was undisturbed, the richness of the pay dirt rapidly 

 decreased until it equaled the true average of the whole deposit, thus 

 showing that the result at first obtained was only a "rim-rock prospect." 



The richest layer in the pay gravel was rarely on bed-rock, but usually 

 from 10 to 20 inches above it, forming the upper surface of the stratum of 

 compact clayey gravel mixed with fragments of decomposed bed-rock 

 which had caught and retained the greater portion of the gold. 



The gravel-bars along French Creek, for several miles above and 

 below the stockade, were examined wherever there was the slighest indica- 

 tion or probability of gold existing in paying quantities with results similar 

 to those already given, and, as might be expected from the level character 

 of the valley, the gravel deposits were richest around its head branches, 



