478 GEOLOGY AND MINING INDUSTEY OF LEADVILLE. 



shaft was cut through the bottom of the ore horizon into underlying White 

 Porphyry. Explorations have not been carried far to the northward on 

 this ground, owing to the steep dip and great influx of water. Probably the 

 yield of the ore did not seem to justify the expense that would be necessa- 

 rily incurred in putting up a pumping plant capable of handling the water. 



On Section G the continuation of the ore horizon to the north has been 

 represented as unreplaced limestone, simply because it has not been proved 

 to contain vein material, though it is impossible to say whether it does or 

 not until it has been actually explored. 



Dunkin mine. — The Dunkin claim lies next east to that of the Climax. 

 From it a large amount of rich ore has been obtained, and exclusively from 

 the continuation of the northern shoot, observed in the Climax ground. The 

 eastern continuation of the main ore shoot of Fryer Hill, which lies on the 

 north flank of the porphyry dike, has, as the map shows, been entirely eroded 

 off the Dunkin ground and the claims to the south of it. Whether the 

 outcrop of the porphyry dike is entirely wanting between the Amie and 

 the northeast corner of the Big Pittsburgh claim, as represented on the map, 

 is not known, since there ai-e no underground explorations in this area from 

 which data may be obtained. It is most probably continuous in depth, but 

 has not been indicated as outcropping, on the principle of representing as 

 far as possible only what is actually known. The great breadth of outcrop 

 of the ore horizon on the Dunkin ground is due to the fact that it lies along 

 the crest of an eroded anticline. There is some evidence to show that in 

 some part of the area covered by this outcrop patches of White Porphyry 

 still remain between the vein material and the Wash, but it is not sufiiciently 

 definite to locate or outline these patches, and their existence does not inval- 

 idate the general truth of the structure, as given by the outlines on the map. 



The Dunkin mine is opened by three shafts. No. 1, at the south end; 

 No. 2, in the middle ; and No. 3, at the north, as shown in Section D. 

 Besides these is an old No. 1 shaft, which, being in an area of barren vein 

 material, is no longer used. The main working shaft is No. 2, near the 

 center of the claim, as well as of ore developments. From this three sets of 

 levels are run, at 10,425, 10,405, and 10,357 feet elevation, respectively. 

 The Wash was here 90 feet and the ore liorizon 40 feet thick, the first level 



