108 GEOLOGY OF TONOPAH MINING DISTRICT, NEVADA. 



know of any water or water signs, while to the north, in the hard rock, water 

 zones outcrop in various places, both on and beyond the area mapped. The 

 explanation of this is probably that the porous breccias and tuffs absorb the 

 scanty precipitation like a sponge. 



Even where rigid fractured rocks outcrop, the scanty descending water 

 normally sinks as through a sieve, using itself up in kaolinization, the formation 

 of limonite, and other hydration processes, and moistening the dry rocks with 

 interstitial water. Fresh rock taken from the Fraction and other shafts in frosty 

 weather was observed by the writer to steam vigorously in the cold air, though 

 the mines are perfectly dry. It is doubtful if there is enough of this water left 

 to form a standing body of ground water at any depth. Where, however, 

 kaolinization and other processes have formed clay seams, the water ma}" be 

 detained and even stored at any depth from the surface downward; and other 

 impervious rock materials may operate in the same way. 



