84 THE AURIFEROUS GRAVELS OF THE SIERRA NEVADA. 
Secret Caiion, consists of a hard, gray quartzite, which seems to be a metamorphic form of a rather 
coarse-grained, quartzose sandstone. The bed-rock at Sterrett’s Claim, on the left bank of Sailor's 
Cafion and two miles in a straight line from its mouth, near Canada Hill, is a hard slate striking 
N. 35° W., and dipping to the northeast at an angle of 85°. 3ald Mountain, a little east of 
Canada Hill, is entirely made up of an enormous mass of impure quartz-rock. The boulders in the 
main channel at Canada Hill consist very largely of quartzose sandstone, and there is in the adja- 
cent region a great deal of this material. The slates and sandstones about Canada Hill have a 
nearly east and west strike. In Miller’s Defeat Cafion, about three miles south of Canada Hill, 
the boulders are largely of sandstone. At Yule’s mine at Startown, near Last Chance, and five 
miles west-southwest of Canada Hill, the bed-rock varies more or less in character from a soft and 
light-colored slate, to a very hard and dark-colored material, which may be either slate or sand- 
stone ; much of this rock is very quartzose, as well as compact and hard. The strike of this rock 
is pretty uniform in direction, a little to the west of north. The rocks in the bottom of the cafion 
of the North Fork of the Middle Fork of the American River, below Last Chance, are metamor- 
phic slates, dipping at a high angle to the northeast, and striking northwest. 
A great deal of the bed-rock in the claims near Michigan Bluff is a very talcose slate ; some of 
it, as at Byrd’s Claim, is a kind of semi-serpentine, mixed with very soft talcose slate. In this 
vicinity the strike of the slates is about north and south, and they stand nearly vertical. There is 
a region, extending for many miles north from Byrd’s Valley, among the forks of Shirt Tail Cafion, 
through Brimstone Plains, and Green Valley, as before noticed, where the bed-rock is almost ex- 
clusively serpentine. There is a fine locality of this rock, on the line of McKinstry’s ditch, south 
of the North Fork of the American River, nearly east of Clipper Gap, and about a mile northwest 
of the ‘‘ United States House.” The extent covers an area of 150 feet wide by 300 or 400 feet long, 
over which the quality of the rock is good ; but the whole mass is much larger. The stone is 
very beautiful, but more or less seamy. At El Dorado Hill the bed-rock is generally a talcose, 
and very soft and thin-bedded slate, striking a little to the east of north, and with a variable dip, 
as if it had been locally disturbed. 
At Smith’s Point, between First and Second Brushy cafions, near Yankee Jim’s, the strike of 
the slate bed-rock is N. 10°—-15° W. The slates vary from talcose to argillaceous, and stand 
nearly vertical. At the Dardanelles Claim, a mile and a half southwest of Forest Hill, the bed- 
rock strikes N. 35°—45° W., and stands nearly vertical: some of it is quite hard, and other 
portions are very soft. ‘ 
In the Illinois Cafion, near Georgetown, six miles south of Forest Hill, the bed-rock is slate, 
which is sometimes very thinly laminated and taleose, while other portions are heavy-bedded and 
argillaceous, so as to pass into a fine-grained sandstone. The more talcose slates are full of cubes 
of pyrites, and these are said to be rich in gold. The rock is all thoroughly decomposed. These 
slates have a strike of N. 20° W., and dip to the northeast at an angle of about 55°; they are 
traversed by a system of joints, underlaying to the southwest at an angle of 45°. At Georgia 
Slide, near Georgetown, the bed-rock is a rather soft, decomposed slate, generally more or less 
talcose, and full of decomposed crystals of pyrites. Bald Mountain, between Caiion and Otter 
creeks, three miles north-northeast of Georgetown, is a mass of serpentine, which does not extend 
far to the east, being succeeded by slates in that direction. At Flora’s, two miles west of Volcano- 
ville, and a little over five miles north of Georgetown, on the extreme end of the spar between 
Republican Cafion and the Middle Fork of the American, the bed-rock is quite hard: it has a 
nearly north and south strike, and stands almost vertical. At the Buckeye-Sucker Claim, about 
one third of a mile southeast of Mount Gregory, near the head of Otter Greek and eight miles 
northeast of Georgetown, the bed-rock is a soft decomposed slate striking about N. 5° W. and 
standing nearly vertical. There is a very heavy body of serpentine in the vicinity of Hotchkiss’s, 
at the southeast foot of Mount Oliver, which is about three miles south of Bald Mountain, and 
some of the same rock at Volcanoville. Serpentine is known to the miners in El Dorado County 
and the southern part of Placer as “ hornblende rock.” 
