MOUNT JACKSON AND HILLS NORTHEAST. 
Df the rocks, occur but do not seem to be of large throw. The Siebert 
lake beds and the later lavas are practically horizontal, their eleva- 
tion being attended only by minor flexing and faulting. 
ECONOMIC GEOLOGY. 
The prospects of the Cuprite mining district, in which the first 
locations were made early in 1905, lie in a belt 1 mile wide which 
extends from a point 17 miles south of Goldfield westward to Mount 
Jackson. The mines are from 2 to miles west of the stage and 
iiitomobile road between Goldfield and Bullfrog. 
The properties of the Goldfield-Midway-Bullfrog Mining Com- 
pany and the Tri-Metallic Mining Company may be taken as types 
3f the Cuprite mining district. The Copper Bell shaft of the first- 
named company, 85 feet deep, is located on the side of a gentle valley 
n Cambrian sedimentary rocks 2 miles south of west of Cuprite, 
rhe shaft is being sunk to encounter a vein which strikes X. G0° E. 
ind dips from 80° to 85° XW. This vein has been traced by means 
)f prospect holes at least 1,000 feet. At one prospect hole the vein 
s capped by a gossan of spongy limonite 9 feet thick. At this depth 
nalachite and less azurite are associated with the limonite and at 
he bottom of the hole, 9 feet deeper, the vein is reported to have run 
2 per cent copper, with 14 ounces of silver and $1.20 in gold per 
on. The vein is from 2 to 5 feet wide and on its borders shows a 
radual passage from totally unaltered limestone to pure limonite. 
me limonite, on the border of the vein at least, is a replacement of 
he limestone. The same company has an incline 65 feet deep situated 
n a shear zone which strikes X. 85° E. and dips 60° S., cutting prac- 
cally horizontal limestone. A streak of ore 1^ to 2| feet wide, trace- 
Die more or less continuously for 900 feet, occupies the shear zone, 
he ore consists of malachite, azurite, and limonite associated with 
eavily limonite-stained chalcedony of conchoidal fracture. The sul- 
hides are chalcocite and less chalcopyrite and pyrite. The two latter 
re undoubtedly original. A number of assays of the ore are said 
» have averaged between 9 and 10 per cent of copper, while the 
lver values are variable, reaching as high as 400 ounces per ton. 
Ividently the silver is intimately associated with the copper min- 
als, the iron compounds giving no silver returns. The average ore 
ins about 1 ounce of silver per ton to 1 per cent of copper, while 
Did is present in traces only. Another prospect on this property 
in limestone much stained by limonite. Malachite and less azurite, 
ith an intensely limonite-stained chalcedonic quartz, occur in small 
dneys throughout the limestone and in narrow seams along joint 
lanes. Chalcopyrite is reported from the surface here, but is not 
loundant, In another prospect irregular lenses of the same ores and 
Ijigues lie in a narrow shear zone in the limestone. Small bunches 
i chalcopyrite are sporadically distributed in the dark chalcedony. 
