COPPER ORE-WHITE GRANITE—IGNEOUS ROCK. 
69 
granite hills at the summit appears to he filled in, to a depth of 100 feet or more, by an 
accumulation of gravel or detritus of granitic rocks. The same formation skirts the foot of the 
opposite high hills, extending at their base in a long terrace. This is on the south side of the 
long southwest and northeast valley of the pass, which is reached from the summit by an 
abrupt descent of about one hundred feet. The terrace has an even, sloping outline, and is 
evidently the remnant of a slope that originally extended throughout the valley between the 
mountains, and filled in between them, in the same way that drift materials of the slope of the 
Great Basin now fill the valleys and cover the irregularities of the underlying granite and 
other rocks. 
Trap dyke .—A short distance from the summit the valley turns around the base of a hill ot 
granite. This hill is traversed by a narrow dyke of trap rock of a dark-green color, but it is only 
slightly exposed in the bank of the stream, and its upper portions are so much covered by 
debris that I did not ascertain its direction. 
Vein of copper ore .—But a short distance from this dyke a vein of copper ore appears on the 
surface. Its presence is indicated by the green color of the carbonate, and it has been prospected 
by parties from Los Angeles, who have broken off some of the surface rock, and accumulated 
several hundred weight of ore. 1 
The general course of this vein was found to be about 45 degrees east of north, and its dip was 
nearly vertical, or appeared so at the surface. The exposure is about 90 feet above the bed of 
the stream. The ore is associated with quartz, and may be found in strings and veins over a 
width of more than fifteen feet. 
Before reaching this locality ot copper ore, outcrops of igneous rock were found on the left. 
A part of the ridge is quite red, and it is over 2,000 feet wide. A small isolated hill on the 
right appeared to be eruptive rock also. 
White granite .—The mountains on the left of this part of the pass are high rugged peaks, 
composed of light-colored granite, in which hornblende is seldom present. The decomposition 
of this granite appears to be rapid, and its surface becomes as white as chalk ; so that wherever 
it is visible between the thick growth of dwarf oaks it looks like patches of snow. When a 
high wind blows over these hills it raises a cloud of white dust, formed by the disintegrating 
feldspar. The granite seems to be almost wholly formed of white feldspar or albite ; and both 
quartz and mica are in small proportion, and are also very white. 
Outcrop of sandstone strata .—A shprt distance below the copper vein, the upraised and uneven 
edges of stratified sandstones and conglomerate become visible on the right side of the pass, 
beyond the low foot-hills of granite. The dark-colored ridge of volcanic rock also shows its 
summit at several places. These formations appear to extend nearly parallel with the valley, 
and the intrusive rock comes down to the bed of the stream. Below this the outcrops of 
upraised strata were nearer to the trail and more distinct, and are seen to be worn into fantastic 
shapes. A mass of one of the outlying beds on the top of a hill had an outline bearing a close 
resemblance to the features of a man. This is represented in the annexed engraving from a 
sketch by Mr. Koppel. It was taken from the camp-ground on the border of the creek in the 
valley of the pass. The cottonwood trees had been scorched and partly burned by fires. 
There was not a good opportunity to examine the lithological character of these strata ; but 
they had the appearance of being nearly identical in their nature with the sediments seen in the 
1 See description of this ore in Chapter XX. 
