54 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA. 
of General Thomas Camp, their strike coinciding with that of the 
Cambrian rocks. The largest masses reach a thickness of 25 feet. 
Similar dikes cut Cambrian rocks north of the summit on the road 
from Alkali Spring to Silver Peak. 
Pieces of greenish-black serpentine are common on the hills formed 
of the older alluvium, although the rock was not seen in place. Under 
the microscope the magnetite and hematite masses associated with the 
serpentine are seen to be lacking in certain areas, and the texture 
rather suggest s that of an igneous rock. In the Silver Peak quad- 
rangle Turner" found a small mass of serpentine in the Lone 
Mountain foothills. The original rock of each of these occurrences 
was probably a pyroxenite, genetically related to the diorite. 
The diorite and diorite porphyry are probably of post- Jurassic 
and pre-Tertiary age. 
STRUCTURE. 
The Cambrian rocks are strongly and complexly folded. The 
axes of the main fold- course east of north; those of the minor folds, 
east and west. The folding is particularly intense along the border 
of the area here discussed. Fan folds and isoclinals are common, and 
in many places these are arranged en echelon. Numerous minor faults 
and zones of brecciation occur in the Cambrian rocks, but faults of 
large throw were not noted. The injection of the Lone Mountain 
batholith lias induced in the near-lying sediments a strike parallel to 
its boundary. 
While it is probable that the Cambrian rocks were somewhat folded 
prior to the intrusion of the granite, the major folding can probably 
be referred to that intrusion. The position of the older alluvium, 
300 feet above the Recent alluvium deposits, shows that the range 
was considerably uplifted in Pleistocene time. 
ECONOMIC GEOLOGY. 
The location of the General Thomas mine, the property of the 
Tonopah-Belcher Mining Company, is shown on the map. When 
visited by the writer (June. 11)05) the mine was (dosed down. Sev- 
eral inclines follow the steeply dipping beds of limestone and shale, 
into which in the vicinity are injected sheets of diorite 1 porphyry] 
Cerussite. malachite, azurite. and chrvsocolla in limestone, heavily 
stained by limonite, lie on the dump. The gypsum associated with 
the ore was evidently formed simultaneously with these secondary 
minerals. Galena and pyrite in calcite were the only original sul- 
phides seen, but some copper sulphide must also occur. Lakes h states 
that lenticular bodies of " sand " carbonate of lead, containing nodules 
of unaltered galena, lay along the contact of porphyry and lime] 
"Turner, Ii. W.. Silver Peak folio; unpublished. 
b Lukes, Arthur, Min. and Scl. Press, v.!. 88, 1904, p. 246. 
