ROCK FORMATIONS OX FRYER HILL. 447 



Before proceeding to a detailed description of the individual mines, it 

 may be well to mention briefly the locality and manner of occurrence of 

 the main rock masses observed on Fryer Hill. 



Gray Porphyry. — The bodics of this roclv found ou the hill have been indi- 

 cated without any direct connection, simply from the fact that it has not been 

 possible in the present state of development to trace each connection defi- 

 nitely, although it is very probable that many of the intrusive bodies may 

 have a common origin. The principal body is that which is shown along 

 the eastern and northern limits of the map, which is all that remains of the 

 main sheet of Gray Porphyry, developed in such thickness in Little Stray 

 Horse Park. It is the oi'dinary gray, somewhat decomposed rock, and has 

 been proved in the Winnemuck shaft of the Little Pittsburgh, in several of 

 the small shafts along the northern edge of the hill on the slopes of Big 

 Evans gulch, and in all the shafts on the eastern edge of the map and imme- 

 diately beyond it. 



The second is a dike-like body, which extends probably from the Lee to 

 the Chrysolite, although its continuity in a portion of this distance, between 

 the Pittsburgh and the Amie claims, has not been definitely proved. This 

 would seem to belong to the type of inteiTupted dikes, as it only reaches 

 the surface in certain points, whereas in others the ore bodies extend con- 

 tinuously over it, but in depth it is doubtless continuous through its whole 

 length. Where cut entirely through, it has an average thickness of forty- 

 five to fifty feet. It is generally so decomposed that it is simply a soft, 

 clayey mass, its only distinction from masses of White Porphyry in a sim- 

 ilar condition being its mottled appearance, due to the forms of feldspar 

 crystals and to iron stains resulting from the decomposition of hornblende 

 and biotite. Occasionally, however, the characteristic large feldspars are 

 distinctly visible, although the mass is so thoroughly altered that the press- 

 ure of the hand suffices to reduce it to a shapeless mass of plastic clay. In 

 general this body seems to have a dip of about 45° to the northeast. 



The third important mass of Gray Porphyry occurs within the lower 

 White Porphyry, and has been cut in a drift connecting New Discovery 

 No. 1 with New Discovery No. 5, and in the grounds of the Chrysolite 

 between Vulture No. 1, Vulture No. 2, and Colorado Chief No. 2; in each 



