The gold quartz veins of Grass Valley, California

The gold quartz veins in the vicinity of Grass Valley, Calif., have been actively mined since the fifties of the nineteenth century. Lindgren mapped the areal geology and studied the mines of the district in 1894, and the accompanying geologic map (pl. 1) is reproduced from his reports. Since then the principal
mines have been deepened, many miles of underground workings have been opened, and new veins have been found.