

BED-ROCK SURFACE: PLACEE COUNTY. 



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is occasionally, but rarely, seen in California, although common enough in some other districts 

 where metamorphic slates occur. At Irish Hill, three miles northwest of Muletown, the bed-rock 

 is also slate, but harder than at the latter place. Among the gravel hills adjacent to Irish Hill 

 the bed-rock is completely decomposed into clay. Some of it is mottled with various colors, — 

 brown, red, violet, purple, yellow, and pink ; other portions are pure white, resembling the rock at 

 Michigan Bar, In the bed of Dry Creek, below Dry Town, there is a large amount of pebbly con- 

 glomerate and line breccia, both highly metamorphosed ; this is seen extending over a distance of 

 between two and three miles, along the course of the Creek, beginning a mile below the town. At 

 the town the rock is chiefly thinly-bedded argillaceous slate, with some harder and thicker-bedded 

 varieties intercalated. At the Potosi Mine, on the south side of Dry Creek, the rocks are argillaceous 

 slate, which is not very hard, but nearly black and containing more or less iron pyrites disseminated 

 through the mass. These slates stand nearly vertical, or have a very high dip to the northeast. 

 They are very much bent and broken, especially near the surface, and are very thin-bedded. At the 

 " Old Amador " or "Little Amador" Mine the hanging wall of the- vein is a rather hard, compact, 

 fine-grained crystalline rock (metamorphic sandstone?) idled with sulphurets distributed through it 

 in very fine particles. It is green in color and called here "greenstone." * The foot-wall of the vein 

 at this mine consists of the usual dark-colored, thin-bedded, fine-grained argillaceous slates. At 

 Down's Mine, the most northwesterly one worked in 1871 at Sutter Creek, the country rock is a 

 greenish slate, generally not very hard, and containing more or less pyrites disseminated through it. 

 It is called " granite " by the miners. The bed-rock in the neighborhood of the great quartz mines 

 of Amador County is mostly of the kind indicated above,' — argillaceous slate, sometimes talcose, 

 varying in hardness, and containing much pyrites disseminated through it. 



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2. Bed-Bock Surface under the Gravel. 



At Iowa Hill the surface of the bed-rock is often very rough and irregular. At Metcalf s Claim, 

 Independence Hill, the bed-rock is exceedingly rough. At Elizabeth Hill the bed-rock is very 

 uneven. At Nahor's Claim, in Green Valley Gorge, the surface of the bed-rock is smooth and 

 water-worn. 



At the Mountain Gate Tunnel, near Damascus, the surface of the bed-rock is remarkably smooth 

 and regular ; pot-holes and projecting points of rock being almost unknown. 



In the Morning Star Mine, at Startown, the bed-rock is very rough ; that is, uneven, with 



many irregular depressions ; and it is generally in these depressions that the miners find the richest 



spots. 



In the Eorest Hill ridge the bed-rock has generally a pretty even surface. It is, indeed, more 

 or less rolling ; but it is rare that points project more than seven or eight feet above the general 

 level. 



At Smith's Point, between First and Second Brushy canons, the surface of the hard bed-rock 

 where exposed, shows little channels cut in it by the water, in the form of furrows, which are 

 sometimes a foot deep and eight or ten feet long. There is a general parallelism in these furrows, 

 and most of them run in a direction about S. 75° — 85° W., across the edges of the slates. 



The town or Yankee Jim's is on the southern slope of the southern rim-rock of the P>i<? 

 Channel. In this channel the bed-rock is exposed over a very large area, and its surface is seen 

 to have many long furrows or channels worn into it ; these vary from one to ten feet or more in 

 length, and are generally shallow and narrow, and often somewhat crooked. The great majority 

 of them are parallel with the direction of the main channel, that is, nearly west, crossing the strati- 

 fication of the bed-rock almost at right-angles, At Indiana Hill, one quarter of a mile southwest 

 of here, on the other hand, there are also many of these same furrows to be seen on the washed 



* This rock, which Mr. Goodyear calls a u metamorphic sandstone," may perhaps be a metamorphic 

 volcanic material. 





