This is an extensive area of scattered placers and a few lode deposits in northwestern Sierra County about eight miles northwest of Downieville. It includes the "diggings" not only at Eureka but also at Craig's Flat, Morristown, and Saddleback Mountain.
It is surrounded by a number of famous placer-mining districts: Downieville, Poker Flat, Port Wine, Poverty Hill, and Brandy City. The hydraulic mines here were worked on a major scale from tbe 1850s to the middle 1880s, and then intermittently on a small scale through the 1930s.
The principal Tertiary channel deposits are at Eureka, Craig's Flat, Morristown, and Monte Cristo, the most extensive being at Eureka. They are part of the Eureka channel, an indistinct branch of the Tertiary North Fork of the Yuba River. As in the other nearby placer-mining districts, the chief values were obtained from the lower quartzitic gravels. Some very coarse nuggets have been found here. Bedrock consists of slate and phyllite and several narrow belts of greenstone and serpentine. Several of the high ridges are capped by andesite. There are a few gold-quartz veins, the most productive baving been at the Telegraph mine, which is on a slate-serpentine contact.
Lindgren, Waldemar, 1911, Tertiary grovels of the Sierra Nevada: U.S. Geol. Survey Prof. Paper 73.
Turner, H. W., 1897, Downieville folio: U. S. Geol. Survey Geol. Atlas of the U.S., folio 37, 8 pp.