AIDS TO PROSPECTING. 
Ore deposits of this type are now being extensively worked throuo-h- 
out southwestern Nevada and eastern California. As they have 
many analogies with those of Goldfield and Bullfrog, other impor- 
tant camps will without doubt be developed. 
2. Gold ores in fault zones: At Blakes Camp fret gold has been 
panned from crushed rhyolite along a fault. The iron pyrite was 
probably originally disseminated in the crushed zone. 
3. Gold ores along contacts of Tertiary lavas and Paleozoic lime- 
stone: A quartz vein at Southern Klondike is situated along the con- 
tact of rlryolite with Cambrian limestone. At the Happy Hooligan 
mine free gold occurs in decomposed rock at the contact of basalt with 
Pogonip limestone. 
AIDS TO PROSPECTING. 
Ore deposits in the area under consideration appear to be confined 
to the Paleozoic rocks, the post-Jurassic granitoid rocks, and the older 
Tertiary lavas. Of the Paleozoic rocks the limestones have so far 
been and probably in the future will be the most favorable country 
rocks. As an exception to the above, however, it should be stated that 
the Cambrian quartzite-schist-limestone series in the southern Amar- 
gosa and Panamint ranges contains strong quartz veins. Of the post- 
Turassic granitoid rocks the granites appear to be more favorable to 
re deposits than the quartz monzonites. Of the Tertiary rocks the 
rst and second rhyolites and the andesitic rocks immediately* preced- 
ng and succeeding the second rhyolite have alone up to the present 
ime proved productive. The rhyolites younger than the Siebert lake 
)eds have, however, in two known instances been silicified and 
lightly mineralized. 
The various formations recognized in southwestern Nevada and 
astern California are represented by appropriate colors and patterns 
m the geologic map (PI. I), from which the approximate distribution 
)f the various rocks may be determined. 
In prospecting in the Paleozoic rocks the limestones should be given 
reference. Mining experience in this region indicates that the most 
avorable portions of the limestone are those nearest igneous rocks, not 
nly the larger intrusive masses, but the dikes as well. Such dike- are 
ommon in the Cambrian rocks from Lida to the General Thomas 
amp. The abundance of ore deposits appears to depend almosl 
irectly on proximity to igneous rocks, and to this Cuprite alone seems- 
n exception. Most of the ore deposits in the Paleozoic rocks are 
ound in well-defined quartz veins, but some deposits are marked by 
eavy "gossans" (hydrated masses of spongy iron ores of red or 
own color). 
Bull. 308—07 m 4 
