234 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



up across these beds. It is proved on the south side of the gulch in the 

 Ben Frankhn tunnel and shaft and in the Kid, Burt (M-13), Soda Card 

 (M-20), and other shafts. The Wynan shaft (M-12) has sunk into it 

 through the Parting Quaitzite, while the Eclipse No. 2 shaft (M-8) is still 

 in White Limestone. 



North side of California gulch. — Oil the uortli side of Upper California gulch 

 the Parting Quartzite outcrops at Pigtail gulch and can be traced in a 

 number of prospect holes and in the slide. In the Iron Duke it shows iron 

 ore which deflects the needle. The Frank shaft (L-26) has gone through 

 the White Porphyry into underlying White Limestone. The Charlie P. 

 (L-28) tunnel in Pigtail gulch and the P. I. R. (L-29) and Comstock 

 tunnels run also in White Porphyry, which gradually thins out to the 

 westward between the two bodies of Pyritiferous Porphyry. The Comstock 

 runs in on the contact of this White Porphyry and a thin layer of dark, 

 impure limestone, which dips 15° to the northeast and is considerably min- 

 eralized. From it has been obtained serpentine similar to that found in the 

 Red amphitheater of Buckskin gulch. The lithological character of this 

 limestone gives no definite indication of its horizon. The pi'esence of the 

 serpentine allies it to the White Limestone, but general stratigraphical con- 

 siderations favor its reference to the horizon of the Blue Limestone.^ In 

 either case it is evident that the White Porphyry, as well as the lower body 

 of Pyritiferous Porphyry, is here cutting up across the strata. 



Printer Boy Porphyry. — Lower down the gulcli the portion of Printer Boy 

 Hill included between the Pilot and Mike faults, a wedge-shaped block of 

 ground which seems to have been let down between them, shows at the 

 surface only a body of quartz-porphyry, which is noticeable as being that 

 in which the principal developments of gold ore have thus far been found, 

 those of the Printer Boy and "5-20" mines. This porphyry is generally 

 decomposed and does not correspond exactly to any other found in the re- 

 gion, though somewhat resembling the Gray Porphyry. It has a greenish- 

 gray matrix, owing its color doubtless to the decomposition of bisilicates, with 

 large white opaque feldspars often two to three inches long. Its eastern 

 limits are defined by the Abe Lincoln (1VI-3G), Nightingale (M-33), and 



' Ou the map this limestone is outliiieil, but the blue color has beeu omitted. 



