•±6 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA. 
Klondike, are of this type. These deposits were the most important 
source of ore in the seventies and eighties. 
2. Replacement deposits: In the Cuprite mining district and to a 
less extent in the General Thomas mine, in the Lone Mountain foot- 
hills, the sulphides appear to replace the limestone in irregular masses. 
The Cuprite deposits are at a considerable distance from granite, and 
in these quartz i^ lacking. The same ores are found here as in other 
deposits in the sedimentary rocks, and it is believed that the ore de- 
posits of Cuprite were formed contemporaneously with those of the 
type B 1 by similar waters, which, however, had deposited their silica 
before journeying so far from the granite mass. 
3. Veins along contacts: Deposits along contacts occur in the lime- 
stone along dikes and sheets of monzonite and diorite porphyry in 
the northwestern part of the area mapped, and along a mass of horn- 
blende schist at Chloride Cliff. The porphyries are almost certainly 
pre-Tertiary and the mineral association is so similar to that in the 
deposits already described (B 1 and '2 ) that there can be but small 
doubt of at least a remote genetic relation in the origin of the two. 
The General Thomas and some of the Montezuma prospects are of 
this type. 
1 ERT] \KY DEPOSITS. 
(C) GOLD DEPOSITS IN SILICIFIED MONZONITE PORPHYRY AND RELATED ROCKS. 
Gold occur- at Kawich and Gold Crater, respectively, in silicified 
and kaolinized monzonite porphyry and biotite andesite. When the 
igneous rock was silicified pyrite was deposited in open fissures in it 
and probably partially replaced it. Disseminated pyrite occurs be- 
yond the silicified zone. Copper sulphide is unimportant, and galena 
is apparently not present. Kaolinization i> probably a later process. 
During the surface alteration of the pyrite free gold lodged in the 
cavities of the altered rock and ai Gold ('rater was deposited along 
joint- in the surrounding iron-stained andesite. The quartz-mon] 
zonite porphyry of Shoshone and Skull mountains is similarly silici- 
fied. The ores of Kawich and Gold Crater were deposited by ascend- 
ing hot water- carrying silica in solution, and while the waters were 
similar chemically, it by no means follows that the deposits are con- 
temporaneous, since the country rock in the one case Avas probably 
of Eocene and in the other of Miocene age. • 
(D) DEPOSITS IN RHYOLITE. 
1. Silver- and gold-bearing quartz veins in silicified and kaolin- 
ized rhyolite: At Silverbow, Eden, Cactus Spring, Wilsons Camp, 
Stonewall Mountain, and Wellington vuggy quartz veins, many of 
them with crustification well developed, fill fault fissures, joint 
planes, and cavities of brecciation and solution. These veins grade 
along their strike into zones of silicified rhyolite carrying gold and 
