486 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



horizon has not yet been eroded. It has as yet been but little explored, 

 partly because of its deep covering of Wash and of the great influx of water 

 due to its position on the western rim of the Little Stray Horse Park basin, 

 and partly because the possibilities of the existence here of valuable bodies 

 of ore have not been generally understood The only actual developments 

 thus far made have been by the Surprise shaft, on the May Queen claim, 

 and by the Denver City shaft, on the claim of the same name. The former 

 found vein material directly beneath the Wash, at a depth of 140 feet, con- 

 sisting largely of chert and black iron at the base, with soft, clayey, low- 

 grade ore above. An incline was run, following the pitch of the ore shoot to 

 the southwest, although the dip of the formation is here to the eastward, as 

 was soon shown by the western drifts, which cut the Parting Quartzite 

 beneath the ore horizon. Some good chloride ore was afterwards found by 

 up-raises which reached a higher portion of the horizon. 1 



The Denver City shaft, in the extreme southeastern corner of the map, 

 is nearly on the crest of the moraine ridge which borders Stray Horse gulch 

 on the north. The Wash was here 180 feet deep, beneath which the main 

 sheet of Gray Porphyry was found in a thickness of about twenty feet. Under 

 this was a thickness of some twelve feet of calcareous sandstone and shale, 

 containing some low-grade ore, which was at first supposed to represent 

 the ore horizon, though it is in reality only the irregular parting of Weber 

 Shales left between the Gray and the White Porphyry. The true ore horizon 

 was afterwards struck at a depth of 234 feet, and rich pockets of chloride 

 ore were found in it. It was passed through by the shaft for about fifty 

 feet, ending in a bed of chert, with White Porphyry, so full of chert frag- 

 ments as to be called by the miners a conglomerate, below it. 2 



There is no question that a part of the Blue Limestone is already 

 opened by the works of this mine, but the shaft is located so near the 

 imaginary southeast-and-northwest line, where the lower White Porphyry 

 cuts across the Blue Limestone, separating it into two wedge-shaped por- 

 tions, that there is a possibility that a portion of this horizon may yet be left 



'Since the close of field-work, large and rich bodies of ore are said to have been opened in the 

 Forest City ground, to the east of this claim. 



a These data were obtained from Mr. Robert Bunsen, superintendent of the Denver City mine, 

 since the completion of field-work, and are not the res:ilt of our own observations. 



