Location and History
This is a placer-mining district in eaStern Sacramento County in the vicinity of the old town of Michigan Bar. It extends to the west and south and includes the Sloughhouse area. Included are dredging fields in and near the Cosumnes River. The district was hydraulicked extensively in the 1850s and 1860s. Later it was worked by small-scale methods by many Chinese miners. The Cosumnes River and some of the older bench gravels were dredged in the 1930s and early 1940s. Also some drift mining was done. Fire clay is mined here now. The total gold production is unknown, but it has been estimated to be at least 1,700,000 ounces.
Geology
Eocene gravels interbedded with several layers of clay and thin sands are distributed over the eastern part of the district in the vicinity of Michigan Bar. The gravels are coarse, well rounded, have a sandy matrix, and usually are not too well-cemented. The dredged area is several miles long.
Bibliography
Carlson, D.W., 1955, Sacramento County, gold dredging: California Jour. Mines and Geology, vol. 51, pp. 135-142.
Lindgren, Waldemar, 1894, Sacramento folio: U.S. Geol. Survey Geol. Atlas of the U.S., folio 5, 3 pp.
Piper, A. M., Gole, H. 5., Thomos, H E., and Robinson, T.W., 1939, Geology and ground water hydrology of the Mokelumne area: U.S. Geol. Survey Water-Supply Paper 780.
