CACTUS RANGE, ECONOMIC GEOLOGY. 95 
Paleozoic sedimentary rocks are gently folded in a manner comparable 
probably with the folding f the Stonewall Mountain Paleozoic rocks. 
Minor normal faults were observed in all the Tertiary lavas, although 
they are much more abundant in the rhyolite and other older forma- 
tions than in the younger. The rhyolite in places is tilted at an anal* 
3f 30°, but it was not determined whether the tilting is due to fault- 
ing or to actual folding. 
ECONOMIC GEOLGGY. 
Wellington, formerly called O'Briens Camp, is situated on low 
rounded hills in the southwestern portion of the range, 11 miles 
south of Cactus Spring. Claims were first located in August, 1904, 
aid when visited (July, 1905) several men were doing development 
work. 
The country rock, the earlier rhyolite, is considerably kaolinized 
and silicified in the vicinity of the veins and is heavily stained by 
limonite. The rhyolite is apparently cut by dikes of altered biotite 
mdesite of purple color. Both rocks along a zone striking N. 70° E. 
ire cut by quartz veins, many of which strike parallel to the exten- 
sion of the zone and dip northward. The larger veins are from 
2 to 4: feet in width. Connecting these are numerous quartz stringers, 
which course in all directions, in many places cementing crushed por- 
tions of the rock. The quartz is semitransparent, crystalline, and for 
he most part white, although locally intensely stained by limonite and 
manganese dioxide. Vugs with small quartz crystals are very com- 
mon, as is also crustification. Minor veins of calcite were observed. 
Differential movement has occurred parallel to- some of the veins. 
incl much of the quartz is intensely brecciated, while minor faulting 
icross the strike was noted in several places. Microscopic examina- 
tion shows that the brecciated fragments were first rimmed by fringes 
if quartz, the interstices being later filled by calcite and limonite. 
rhe values reported are largely gold, silver constituting but one- 
wentieth of the assay value. The ore is free-milling and the gold 
s in close association with limonite. The quartz and the contained 
>res were deposited in joints in the interstices of breccia and along 
mall and possibly large fault fissures. The veins have been faulted 
nd the quartz crushed. Only ores oxidized by surface waters have 
ts yet been encountered. 
| The Cactus Mining Company has a shaft in silicified rhyolite 
hree-fourths of a mile south of Cactus Spring. Coarsely crystal- 
ine white quartz veins, with many vugs, cut the rhyolite, and, 
hese on surface outcrops are heavily stained by iron compounds, 
fyrite and chalcopyrite are sparingly present in the quartz and 
) a less degree impregnate the surrounding rhyolite. Free gold i 
sported. Both fissure filling and replacement of the country rock- 
