SILVER, LEAD, COPPER, IRON, SALT. 97 
extensive and rich placers, which only require abundance of water and the facilities which would 
be afforded by a railroad to become sources of national wealth. The exploration of the Armagosa 
veins and of the surrounding country, not only for veins, but for placers, is exceedingly desirable. 
Placers and veins of San Francisquito and the vicinity.—Gold has been obtained for several 
years past in the lower portions of the mountains north and northwest of Los Angeles. It 
occurs in veins and in placer deposites ; but the explorations have hitherto failed to develop 
riches comparable in quantity to those of the placers of the Sierra Nevada. The talcose and 
auriferous slates are found in extended ridges along the lower part of the Pass of San Francis- 
quito, and it is probably from these that the gold is derived. Similar rocks occur, also, at the 
base of the mountains where they are crossed by the Cajon Pass; and it is probable that gold 
can be obtained there by washing in the beds of the streams. Mr. Marcou states that he saw 
rocks in the pass precisely similar to those found between Rough-and-Ready, Grass Valley, and 
Nevada City, which contain veins of auriferous quartz.* To me the rocks of the lower portions 
of the pass appeared to be chiefly metamorphic, while those bearing the quartz veins at Grass 
Valley and vicinity were evidently in great part of erupted greenstone. The specimens which 
Mr. Marcou notes as coming from the Cajon Pass were most probably brought through there 
from the Armagosa mines in the Great Basin. 
SILVER, LEAD, AND COPPER. 
These metals, or their ores, do not appear to have been met with in any quantity along the 
route. The only specimens in the collection are of copper ore from Placer mountain, and 
are probably from the mine noticed under the head of ‘ Gold." The ore is noticed in the 
description of the collection (No. 92.) It is chiefly silicate and carbonate of copper dissem- . 
inated ima gangue of a beautiful light-colored garnet, which is both massive and crystalline, 
fine crystals being found on the interior of small cavities. The copper ore mentioned by Lieut. 
Abert is, according to his observations, associated with carbonate of lime. These specimens 
are, therefore, most probably from another locality. 
According to Wislizenus, copper occurs at many places in that region, and he cites the fol- 
lowing as localities: Las Tejeras Jemez, Abiquiu, and Guadelupita de Mora. He, however, 
knew of only one locality that was worked—that south of the placers ? 
Vein in the Great Basin.—A vein of copper ore, with a width of several feet, occurs on the 
northern side of the Bernardino Sierra, not far from the entrance to Williamson's Pass. It is 
about seven and a half miles east of Johnson's river, so named on Lieutenant Williamson's 
map. The rock which bounds the vein on each side is gneiss or mica-slate, trending nearly 
N. 75° E., and the dip of the rocks and vein is nearly vertical. The outcrop, showing dark- 
green stains of the carbonate of copper, varies from twenty to thirty feet in width. The vein- 
stone is chiefly quartz. A large amount of oxide of iron filling the cavities shows the former 
presence of a very considerable amount of sulphuret of iron, now entirely decomposed.* Cop- 
per ore also occurs in the pass, (Williamson’s Pass,) a few miles below the summit. 
The occurrence of silver with the gold obtained by crushing and washing the copper ores 
of the mine in or near the new placer is mentioned by Lieutenant Abert. It is possible that 
brilliant white particles-of mundic may have been mistaken for the metal; but it would not be 
strange to find the silver there, as we are informed of the presence of veins of lead ore, one of 
its most common associates. I do not find any full account or description of this lead mine. 
According to Lieutenant Abert, the vein is in the limestone, and he gives a figure of a Tere- 
bratula, a fossil common in the carboniferous limestone which he obtained in the mine. 
The carboniferous limestone appears to be peculiarly favorable to the occurrence of lead ores 
and silver. Rich veins are found in the Organ mountains, about 200 miles south of the route, 
! Resumé, p. 48. 2 Wislizenus. Memoir of a Tour through Northern Mexico, p. 
3 A notice of this vein was given in the author's Preliminary Geological Report, p. we iui will appear with further 
details in the final Report. 
