The Richardson area is characterized by gentle slopes and broad, alluvium-filled valleys (Prindle and Katz, 1913, p. 140). The area is unglaciated and largely overlain by windblown silt, sand, and loess, locally up to 50 meters thick (Foster and others, 1979). The bedrock in the region comprises greenschist to amphibolite facies schist, marble, and gneiss that have been intruded by various igneous bodies (Bundtzen and Reger, 1977, p. 29). The schist and marble are probably Paleozoic, and the gneiss has a probable protolith of Precambrian and Paleozoic sedimentary and igneous rocks (Weber and others, 1978). Some quartz veins in the schist and gneiss are mineralized (Chapin, 1914). The intrusive bodies in the area range in composition from rhyolite to andesite. Fine-grained rhyolite containing quartz and feldspar phenocrysts is common throughout the area (Olson and others, 1985). At the nearby Democrat Lode (BD014), the rhyolite contains arsenopyrite, gold, and pyrite, and is albitic, clay, and sericite altered (R.J. Newberry, oral communication, 1998). Structurally, the Richardson region is cut by a northwest-trending fracture system termed the Richardson Lineament. The lineament appears to correspond with the distribution of the rhyolite and other intrusive bodies and placer gold deposits (Bundtzen and Reger, 1977, p. 29). Also, the lineament tends to separate gneissic rocks to the northeast from schistose rocks to the southwest (Swainbank and others, 1984).
The Democrat Creek placers are located on a section of the Richardson Lineament termed the Democrat dike. Bedrock in the Democrat Creek drainage is composed primarily of biotite gneiss and rhyolite. The gold source for the residual and fluvial placers of Democrat Creek is interpreted to be the rhyolite. The rhyolite has an aphanitic groundmass, and quartz, plagioclase, and K-spar phenocrysts. Locally, the plagioclase phenocrysts are weathered to clay, possibly montmorillonite. Albite accompanies quartz in the veins (R.J. Newberry, oral communication, 1998). Quartz stringers locally containing sulfides are also present (Olson and others, 1985). The lode contains fractures with Fe-stained void-space quartz veins and localized sericite. K-spar from the rhyolite yielded a K-Ar minimum age of 86.9 +/- 2.6 Ma (Bundtzen and Reger, 1977). Minerals in the rhyolite are arsenopyrite, gold, pyrite, and stibnite (McCoy and others, 1997). Metz and Hawkins (1981) reported the average gold fineness to be 928.Gold was first discovered in the Richardson district in 1905. Placer mines began operating in several streams in the immediate area. These include Tenderfoot Creek (BD039), Banner Creek, and Buckeye Creek (BD005) and associated tributaries. After peak gold production in 1908, mining in the area declined (Olson and others, 1985). From 1905 through 1921, production from the Richardson district was approximately 95,000 ounces of gold and 24,000 ounces of silver (Bundtzen and Reger, 1977). Since 1980, the district has produced approximately 10,000 additional ounces of gold from intermittent mining (Olson and others, 1985). Because of the depth to bedrock, mining along Democrat Creek has primarily used open-cut methods (Ellsworth and Parker, 1911). Recently, limited placer mining has occurred in association with the development of the Democrat Lode (BD014).