96 



THE AURIFEROUS GRAVELS OE THE SIERRA NEVADA. 



vertical from top to bottom. The gravel is a mixture of all sorts of metamorphic rocks, with but 

 little quartz, and few large boulders. Many of the pebbles soften on exposure to the air. 



At Todd's Valley the gravel ranged from a few feet to thirty or forty in thickness, and nine 

 tenths of the pebbles and boulders of which it is made up are of quartz. They are not so much 

 water- worn as is usually the case in deep gravel ; indeed, the deposit has a more or less brecciated 

 appearance, and there are streaks of the angular gravel so firmly cemented together by oxide of iron, 

 that it will break through the centres of the quartz pebbles rather than crumble. Over the gravel 

 lies a stratum from twenty to twenty-five feet in thickness of bluish-gray sand, and above this 

 some thirty or forty feet of volcanic cement. This cement is soft and breaks into lumps, which 

 pass easily through the sluices. The proprietor thinks that there is gold enough in the gravel to 

 pay for handling 150 feet in thickness of this cement, if water were free. 



At the Reed Claim, on the north side of Mameluke Hill, near Georgetown, the banks have a 

 maximum, height of fifty or sixty feet. On the bed-rock there was a thin layer of gravel ranging 

 from a few inches to two or three feet in thickness. This has been all drifted out, and is said to 

 have been extremely rich. At this point the surface of the bed-rock pitches southerly into the 

 hill, and the southwest slope in the front of the claim was very rich, and is reported to have paid 

 in spots as much as a thousand dollars per hour. From the area covered by a 4 x 4 foot shaft the 

 sum of $ 7,000 was once taken. The gravel contains considerable quartz, which appears in general 

 to have been but little washed. Immediately above the gravel comes a stratum of soft, gray, de- 

 composed, volcanic bouldery cement, varying from ten to fifty feet in thickness. Over this there 

 is another streak of quartz gravel, with small pebbles generally but little washed ; this stratum is 

 from one to four feet thick and contains a little fine gold. Above this there are a few feet of ir- 

 regularly alternating layers of gravel, volcanic ash, and red dirt, more or less mixed together, and 

 forming the top surface. 



In the Roanoke Tunnel, about a quarter of a mile east of Bottle Hill, the channel is said to lie 

 some 300 to 350 feet below the top of the crest of the ridge. The gravel is reported as not having 

 averaged over two feet in depth, and as being covered with very hard volcanic bouldery cement. 

 An upper stratum of gravel was found here, about four feet in thickness, which contained some 

 fine scale gold, and ran nearly level from the upper bed-rock, or edge of the rim, through the 

 cement over the deeper channel. The bed-rock is generally hard and dark-bluish in color ; and 

 the gravel consists of pebbles and boulders of dark-colored hard metamorphic rocks, the quantity 

 of quartz being small. 



At the Oak Grove Claim, on the north side of the ridge, a mile and a half east of Volcanoville, 

 several tunnels have been driven, and irregular works extended, from there for some distance into 

 the hill. The gravel here consists of metamorphic materials, which are more than usually mixed 

 with volcanic pebbles and boulders. The gravel is very hard in places ; and the gold, which is 

 mostly near the bed-rock, is not coarse. 



At Flora's Mine, two miles west of Volcanoville, the bank exposed in the hydraulic workings 

 is about 130 feet high, of which the lowest twenty-five feet consists of well-washed metamorphic 

 gravel, which near the bed-rock is generally very hard, but higher up somewhat softer. The next 

 twenty-five feet is a bed of volcanic ash cement, red in color, containing no large boulders, and 

 rarely a pebble of any size, but full of little smooth rounded pellets of volcanic rock, which were 

 once very hard but now considerably softened by decomposition. Over this, the whole bank, to 

 the top, consists of well-worn, bouldery gravel, containing a little quartz and considerable meta- 

 morphic rock, in the form of boulders, as well as a little gold. This deposit, however, is more than 

 half made up of volcanic materials. 



At the Grizzly Flat Mine, half a mile a little east of south from Volcanoville, the character of 

 the gravel is the same as that at Mameluke Hill, it being made up of small fragments of quartz, 

 but little washed. The finer portion of it consists mostly of clayey matter, resulting from the dis- 

 integration of the bed-rock. This material appears in the hydraulic face to be some thirty to 

 thirty-five feet deep, and above it lies red volcanic cement, containing a few hard boulders. 



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