California Mines

Santa Clara River Placers (1910 Mining and Scientific Press)
The Santa Clara river placers are situated about 40 miles northwest of Los Angeles, on the north side of the little Santa Clara river, in Los Angeles and Ventura counties, California.

How We Get Gold In California (1860 Harper's New Monthly Magazine)
...this substance yielded like clay to a few blows of the pick; and as the slices were turned carefully up, they resembled chunks of plumb-cake, the clay being stuffed in every part with the golden lumps. Upon breaking these pieces in the hand like bread, the interior was still found plugged with pellets of gold, and the whole mass was heavy with it.

Trinity River Gravels of California (1911 Engineering and Mining Journal)
The Trinity River region in northwestern California has long been worthily noted for its placer mines, the working of which opened with a rush in the early ’50’s and has continued with more or less regularity ever since.

Dredging for Gold in California (1911 Engineering and Mining Journal)
Article details the gold dredging industry in California as of 1911. Many interesting details are recorded, including that California had at least 61 active gold dredges during that year.