122 



THE AUEIFEJROUS GRAVELS OF THE SIERRA NEVADA. 



vein at this place, the so-called "Reed Lode/' was enclosed, for a portion 

 of its course at least, between walls of argillaceous slate on one side and 

 serpentine on the other. In Salt Spring Valley, a continuation of the 

 depression between the two ranges, previously mentioned, ten or twelve 

 miles northwest of Copperopolis, the rocks consist almost entirely of slates, 

 generally thin-bedded and fine-grained j the prevailing character is argil- 

 laceous, although portions are talcose or chloritic. These slates, with the 

 associated serpentine, appear to occupy the whole width of the valley 

 between the two ranges, which themselves are made up of much harder 

 rocks, evidently highly metamorphosed and probably, as farther south, com- 

 posed in good part of volcanic materials. The chemical changes in these 

 rocks have been carried so far that the stratification is almost or quite oblit- 

 erated, and could hardly be made out at all unless from the peculiar form 

 of the elongated outcrops on the surface, which everywhere on these ranges 

 is but sparsely covered by detritus. At the western base of the Gopher 

 Hills the granite appears at the surface and occupies a considerable width, 

 where crossed by the stage-road from Stockton to Copperopolis. 



Not far from Telegraph City is the locality called Quail Hill, which at one 

 time attracted much attention on account of its supposed richness in gold. 

 There is here a belt of several hundred feet in width, through which the 

 rock has been acted on by chemical influences so as to have become more 

 or less irregularly decomposed, the resulting material, which is of a clayey 

 and ochery character, having assumed a variety of brilliant colors. The local 

 name for this decomposed formation is "calico rock/' The same peculiar 

 belt may be traced at intervals for several miles along the edge of the foot- 

 hills, and being near the granite, which, as already mentioned, occurs in this 

 position, it is not unlikely that the proximity of the eruptive mass is con- 

 nected with the peculiar decomposition of the adjacent slaty rock. This 

 belt of calico rock was at one time believed by some persons to be very rich 

 in gold, and Quail Hill was the scene of considerable excitement in conse- 

 quence of this.* 



On the north side of the Bear Mountain Range, and in close proximity to 

 it, is the belt of rock through which the Great Quartz Vein passes, and which 

 presents many phenomena of interest with reference to the occurrence of the 

 various formations characteristic of the western slope of the Sierra, although 



* See Proceedings of the California Academy of Sciences, Vol. III. p. 349, in which article the 

 whole mass of rock at Quail Hill is stated to be worth $50.22 per ton in gold and silver. 



