The Dulzura district is in southern San Diego County in the San Ysidro Mountains and about 25 miles southeast of San Diego. Placer gold was discovered here in 1828, but the lode deposits were not mined until 1890. The mines were worked sporadically from the 1890s until the 1930s. The principal gold source has been the Donahoe mine; others include the Johnston and Doolittle mines. The district is underlain by granitic rock, quartzite, gneiss, and schist. The deposits occur in a northwest-trending shear zone in metamorphic rock and consist of broken and crushed quartz containing native gold and sometimes abundant sulfides. The deposits are shallow and usually are discontinuous.
Merrill, F. J. H., 1916, Dulzura distrid: California Min. Bur. Rept. 14, pp. 664-665.
Weber, F. Harold, Jr., 1963, San Diego County, gold: California Div. Mines and Geology County Rept. 3, pp. 115-167.