448 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



instance characterized by its mottled appearance and by its more thorough 

 decomposition than the inclosing White Porphyry. This is probably part 

 of the same sheet which crosses the White Limestone under Little Stray 

 Horse gulch, and is cut in a shaft south of New Discovery No. 5, in the 

 New Gambetta shaft, and in the Eudora shaft. New Discovery No. 6 cuts 

 a similar sheet of Grray Porphyry in the Blue Limestone, which evidently 

 is part of the cross-cutting sheet of the Waterloo-Henriett claims. There is 

 little doubt that all these bodies form part of the same intrusive sheet which 

 is gradually rising in geological horizon to the westward, as shown graph- 

 ically on the map. 



Besides these three principal bodies, small irregular sheets are found 

 overlying the iron in the southern portion of the Little Chief claim and in 

 the Robert K. Lee mine, apparently conformable with the formation. In 

 the eastern portion of the latter mine also is a dike-like sheet, five or six 

 feet thick, cutting through the ore bod}' and extending from the northern 

 di-ift on first level to the eastern drift on second level, or in a northwesterly 

 direction, with a dip, however, to the eastward. 



White Porphyry. — The Upper shcct of Wliitc Porphyry is generally very 

 much decomposed, and within fifteen or twenty feet of the ore bodies it is 

 reduced to a mixture of clay and quartz grains. Over the main summit of 

 the hill there is little of it left, probably on an average not more than fifteen 

 or twenty feet. Its decomposed state is evidently due to the abundant 

 action of surface waters, which have free access through the superincum- 

 bent Wash, there being no solid rock above it. 



The lower White Porphyry is relatively much less decomposed, 

 although the microscope shows that decomposition has already progressed 

 to a considerable extent within its mass. In some places, however, notably 

 in the lower drifts of the Dunkin and Climax, where it approaches the lower 

 limestone, it has been reduced to a clay and is so full of oxide of iron that 

 it is difficult to distinguish it from the iron mass which has replaced the 

 limestone. It is also characterized by a laminated appearance which makes 

 it closely resemble decomposed shale. Its thickness has been proved in a 

 number of shafts to vary from sixty to one hundred and sixty feet, as fol- 

 follows: Chmax No. 1, 115 feet; CHmax leased shaft No. 1, 60 feet; Cli- 



