14S The Americati Geologist. 
March, 1890 
A number of small veins are found in the low granite hills 
north of Mono lake. Iron pyrites is abundant, as was univer- 
sally found to be the ease with veins in granite. These veins 
are generally quite flat. 
Bodie has been the great centre of gold mining in eastern 
California, more than $20,000,000 having been produced here. 
The gold bearing veins are unique in many respects. Their 
period of formation followed the volcanic activities of Terti- 
ary time, and in age as well as general character they differ 
markedly from the other important gold deposits of Califor- 
nia. The inclosing rock is hornblende andesite, which covers 
an extensive area north of Mono lake and seems to belong to 
the same period of eruption as the andesites along the summit 
of the central and northern Sierras. The most important thing 
about the Bodie ores is, however, the fact that the veins 
ceased to be profitable below 700 feet. The mineralized zone, 
containing a large number of quartz veins within a width of 
400 feet, extends nearly north and south for about two miles, 
but has been profitably worked only along the northern por- 
tion. The veins are divided into two classes, an older eas- 
terly dipping one, and a younger, nearly vertical or inclined 
at a high angle to the west, one series faulting the other. The 
veins of the Syndicate mine on the north are beautifully 
banded, with the appearance of having been formed in open 
fissures by successive layers from the walls inward. They 
became unproductive at a depth of 250 feet. The Standard 
mine next south shows a still larger number of veins, varying 
from exceedingly thin seams, which are very rich, to an ex- 
treme width of 90 feet. The latter vein has an average width 
of 20 feet according to Whiting and constitutes the most im- 
portant ore body. Mr. Whiting* considers these veins "to 
have been in part a filling of open fissures, in part a gradual 
replacement of thinly sheeted country rock between the prin- 
cipal structural planes of fractured zones by the vein forming 
minerals once held in solution." In the Standard mine the 
veins became smaller and almost barren below the 500 foot 
level. In the Bodie and Bulwer mines on the south the ore 
bodies extended to a somewhat greater depth. The Fortuna, 
the greatest of the older veins of the Bodie mine, became un- 
*Eighth Report of the Cal. State Mining Bureau, p. 338. 
