44 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA. 
generated on the swift streams of the Sierra Nevada. The heat of 
July and August renders surface work in those months almost im- 
possible in the more southern camps. 
GENERAL CHARACTER OF THE ORE DEPOSITS. 
The ore deposits herein described are apparently the work of two 
distinct main periods of mineralization, one post-Jurassic and pre- 
Tertiarv. the other Tertiary. The veins at Chloride Cliff may. in- 
deed, be pre-Jurassic, but their resemblance to the post-Jurassic veins 
renders this questionable. 
POST-JURASSIC AND PRE-TERTIARY DEPOSITS. 
A DEPOSITS IN GRANITE. 
1. Pegmatitic dike-: Dike- of pegmatite at Oak Spring are re- 
ported to carry gold and silver value-. These, so far, have proved 
unimportant. 
-2. Reopened pegmatitic dikes: The quartz, itself of pegmatitic 
origin, has been crushed, and the veins are probably due to the same 
period of mineralization as that which formed the deposits described 
in the next paragraph. The deposits of Lime Point and some of 
those at Trappmans Camp arc of this origin. 
3. Massive quartz veins in fissures, joints, and irregular zones of 
brecciation: The quartz is not crustified. The chief sulphide is pyritej 
although galena, chalcopyrite, and sphalerite occur locally. The 
deposits are usually gold bearing, but with the introduction of ga- 
lena silver values may predominate. The ores were deposited by 
water, which may have been remotely connected with the granitic 
intrusion. The sharp contact with the comparatively unaltered wall 
rock indicate- that these veins filled open fissures. Such appear to 
be the deposits at Old Camp and some of those at Trappmans Camp, 
Oak Spring, and Southern Klondike. The deposits of Goldbelt are 
in quartz monzonite. In the pasl the veins at Old Camp have been 
larg c producers. 
4. Impregnation of pyrite along joints: This is an unimportant 
form of deposit -ecu only at Trappmans Camp. 
B DEPOSITS IN PALEOZOIC SEDIMENTARY ROCKS, PREDOMINANTLY LIMESTONE. 
1. Quartz veins and irregular masses occupying faults, jointSj 
bedding plane-, and 'brecciated zone-, as a rule in the neighborhood 
of granitic intrusions: Rarely a little calcite is associated with the 
quartz. The original sulphides deposited in the quartz include 
chalcopyrite, galena, pyrite, and sphalerite, while telluride was 
probably originally present in some deposits. In the veins in lime- 
stone the predominant sulphides are chalcopyrite and galena and the 
