182 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA. 
ECONOMIC GEOLOGY. 
The ore deposits of Bullfrog have recently been described by 
Ransomed He shows that the ore occurs in and along fault fissures 
in silicified or kaolinized rhyolite. Silicification and kaolinization 
have been important j^rocesses of metamorphism throughout the 
Bullfrog Hills. The areas outside of the region shown on the Bull- 
frog special map so altered are delineated in fig. 4 (p. 43). Both 
the rhyolite and the andesite of the two domelike hills northwest of 
Howell ranch are silicified, and in addition seams of chalcedonic 
quartz fill solution cavities and fault and joint fractures. Other 
areas of silicified rhyolite are situated northwest of Crystal Spring, 
west of Indian Springs, and 4 miles south of east of Currie Well. 
GOLD MOUNTAIN RIDGE AND THE HILLS TO THE NORTH OF GRAPEVINE 
CANYON. 
TOPOGRAPHY AND GEOGRAPHY. 
Gold Mountain, with an elevation of 8,145 feet, is situated on a 
ridge which parallels Slate Ridge. North of Tokop the two ridges 
are connected by low hills. The Gold Mountain ridge lies to the south 
of Oriental Wash and to the east of Death Valley. In the vicinity of 
Gold Mountain the ridge is rugged and steep, being formed of sharp 
peaks and V-shaped valleys. Strikingly distinct from the other 
summits is the basalt-capped butte northeast of Old Camp. A num- 
ber of northeast-southwest ridges northwest of Grapevine Canyon 
are joined to Gold Mountain on the south or are isolated in the desert 
gravels near by. These ridges, which parallel the trend of the Gold 
Mountain ridge, are here included in its description. On the other 
hand, the mountain front north of Grapevine Canyon, northeast of 
Death Valley, and southwest of the California-Nevada line is struc- 
turally an extension of the Amargosa Range. 
The distributive drainage characteristic of arid regions is well ex- 
emplified in these hills. Fragmental material from the Gold Moun- 
tain ridge near the Rattlesnake mine has reached lower levels by three 
distinct channels. A portion of the gravels moved to the southeast 
and found lodgment either around the playa in Grapevine Canyon 
or was washed out into Sarcobatus Flat near Thorp's mill. A second 
portion traveled south 4 miles, north of east 2 miles, and then south 
around the hill at the junction of the county line and parallel 37° 15'. 
The material eventually mingled with that which took the more direct 
route already described. A third portion did not swing around the 
hill just mentioned, but continued north of east into Sarcobatus Flat. 
Probably at any one time but a single channel was used, but in com- 
paratively recent times all three have been iised. 
" Ransome, F. L., Bull. U. S. Geol. Survey No. 303 (in press). 
