

88 



THE AURIFEROUS GRAVELS OF THE SIERRA NEVADA 





It looks as if a body of sandstone, full of the most irregular seams, had had all these filled with 

 chalcedony and jasper, and afterwards the rock had been dissolved away, leaving only the silicious 

 skeleton, in the form of a honey-combed mass. 



On the road from Volcano to Fiddletown, from the crossing of Dry Creek on, the rock is slate, 

 with the regular northwesterly trend and high inclination to the east, On the road from Fiddle- 

 town to Mud Springs, on the hills to the north of Indian Creek, granitic rock occurs, and extends, 

 for a distance of four or five miles, to the edge of the canon of the Cosumnes River ; much of it 

 approaching mica or hornblende slate in character, but with a granitic texture. This rock con- 

 tinues, on the route indicated, as far as the brow of the hill on the south side of the canon, where 

 slates occur, some portions of which have the texture of diorite. These slates, which continue 

 down to the Cosumnes River, have a nearly north and south (magnetic) strike ; but always a high 

 inclination, sometimes to the east, and occasionally to the west. Just below Kingsville, three 

 miles east of Shingle Springs, on the road to Placerville, there is a body of serpentine. The rocks 

 in this vicinity, however, are in general slates and sandstones, in a large proportion of which the 

 stratification is nearly obliterated, although in places there are clay slates of which the bedding is 

 perfectly preserved. There is a ridge between Latrobe and Big Canon Creek, which looks very 

 prominent, as seen from the hills about Placerville. Here the rocks exhibit a great variety of 

 texture, appearing to be metamorphic forms of clayey and sandy beds, and conglomerates of small 

 pebbles. Intercalated with these are beds of what appear to be volcanic materials, looking like 



* 



diorite. Between Latrobe and Michigan Bar, on the Cosumnes, low down on the foot-hills, the 

 bed-rock consists of hard, and much altered strata, the outcrops of which are much elongated in 

 the direction of the strike of the formation, which is about K 15° W. It is only by the form of 

 these outcrops that the bedding can be made out, so complete has been the metamorphism of the 

 original material which seems to have been sandstone. In places, however, there are intercalated 

 masses of thin-bedded argillaceous slates among these more crystalline and perhaps in part volcanic 

 rocks. In the vicinity of Michigan Bar the bed-rock is slate, often much, decomposed and dipping 

 usually at a high angle to the northeast, although sometimes in the opposite direction. 



In the Sugar Loaf, near Puckerville, which is about six miles nearly east of Forest Home, the 

 rocks are metamorphosed and very hard slates, sandstones, conglomerates, and breccias. - At a point 

 about a mile and a half below Puckerville there is a small outcrop of limestone, and the same rock 

 probably occurs, at a point opposite this, on the Cosumnes River. There is also a considerable 

 quantity of imperfect serpentine in the hills, to the southwest of the Sugar Loaf, near Pucker- 

 ville. 



From Dry Creek to Amador Creek the rocks are almost all very hard metamorphic slates and 

 sandstones ; and in many places the stratification is only to be made out from a study of the out- 

 crops, which are elongated in the direction of the strike of the formation. In the vicinity of Ran- 

 cheria Creek there is a large quantity of porphyritic slate, containing large greenish-white crystals 

 of feldspar, and somewhat resembling the " China rock " mentioned as occurring at Greenwood. 

 On, or very near, the crest of the ridge next north of Sutter Creek, about half-way from the town 

 of that name to Volcano, there is a limestone quarry, where this rock has been quarried for burn- 

 ing into lime. The belt, which does not appear to be more than 200 or 300 feet wide, shows at 

 various points along a line of nearly half a mile in length, having a general northwesterly trend. 

 The rock has been shattered and seamed in every direction, and some of the ('racks thus formed 

 have become filled with quartz. This limestone quarry is about six and a half miles from the, town 

 of Sutter Creek, and the bed-rock passed over between the two places consists of slates and schists, 

 somewhat inclined to be porphyritic in structure. Some of the slates are thin-bedded, dark-blue, 

 and argillaceous, and other portions are in heavy layers, or " blocky." 



The bed-rock at Muletown, a little north of lone City, is slate, passing into sandstone, generally 

 much decomposed, and especially so under the gravel. In the adjacent ravines and gulches below 

 the level of the floor of the gravel, it is quite hard. In some of the soft slates in this vicinity 

 there are indications of line lamination or cleavage, at right-angles to the planes of bedding, such as 



