128 THE AURIFEROUS GRAVELS OF THE SIERRA NEVADA. 
The eaiion of the Mokelumne River, between Jackson and Mokelumne 
Hill, in Calaveras County, is about 1,500 feet deep, and the rock exposed 
here is of a gneissoidal character. The river, along this portion of its 
course, has been “flumed”’ again and again; it was long since abandoned to 
the Chinese, and probably has ceased to be worked even by them. The 
detrital formations at Mokelumne Hill were, in the early days, the scene of 
the most active mining operations, and they seem to have been, in places at 
least, extremely rich. Mr. Hittell says, “ Every variety of mining operations 
has been carried on successfully in the neighborhood of Mokelumne City..... 
There is scarcely one of the numerous ravines and gulches in the vicinity 
the bed of which has not been overturned, year after year, since 1849; first, 
with the butcher-knife and pan or datea ; then with the pick and shovel and 
the rocker ; next, with the long-tom; and finally, with the sluices. At last 
they were abandoned to the Chinamen with their rockers, and the Digger 
Indian women with their little crowbars, horn scrapers, and tin pans.” * 
It is said that the claims at Mokelumne Hill were limited to fifteen square 
feet, and that some of them produced as much as 250 pounds of gold each. t 
The gravels in this vicinity were thin, but extremely rich. They were 
covered by a mass of sedimentary volcanic materials as much as 200 feet 
in thickness. This deposit was somewhat variable in character; but gen- 
erally very fine-grained and homogeneous, having a pinkish-red color, and 
breaking with a conchoidal fracture. Over this, again, was a mass of bould- 
ers of lava (andesite?) not polished and smooth as if formed by the action 
of water, but roughly rounded in such a way as to lead to the inference that 
their form was due to dry friction — if the expression may be allowed — of 
a mass of lava broken up on the surface and carried downwards by the 
aid of gravity alone. Large masses of this lava detritus were closely exam- 
ined by the writer, without the discovery of a single pebble of quartz or any 
other form of metamorphic rock. The Mokelumne Hill channel seems to be 
continued for considerable distance to the southwest. Along the borders 
of Chili Gulch, for a distance of six miles from Mokelumne Hill, active 
mining operations were being carried on from 1860 to 1864, and perhaps 
later. Here there were several beds of gravel intercalated in the lava, the 
“ pay-streak”” being at the bottom, however, and about eight feet thick. 
Much of it was so compacted together that it had to be stamped before it 
* Mining in the Pacific States, p. 90. 
tT P. Laur, Métaux Précieux en Californie, p. 27. 
