Bonanza Creek was placer mined for about 2.3 miles of its length above the mouth of Canyon Creek. Tributaries that were also placer mined on the north side of this part of Bonanza Creek, include Skookum Creek, Little Eldorado Creek, Snow Gulch, and Coarse Money Creek were also placer mined (Capps, 1915; Capps 1916; Moffit, 1954; Richter and Jones, 1973). The placers along Bonanza Creek were in the active stream channel and in various bench deposits including abandoned channels over 100 feet above the present stream. The placer concentrates included cinnabar, native copper, galena, molybdenite, and native silver. Much of the gold in the present stream, where gravels are 2 to 12 feet thick, was concentrated on and within the top 1 to 2.5 feet of fractured bedrock. The overburden deposits, commonly frozen, could be over 50 feet thick on the benches (Moffit, 1943). Some of the gold may have been derived from reworking of Tertiary or Quaternary gravels like those exposed on the summit of Gold Hill (Richter and Jones, 1973). However, the mineralogical complexity of the placer concentrates suggests that this is not the only source. The tributaries and upper reaches of Bonanza Creek also rework various younger Quaternary surficial deposits that could be more locally derived. Bedrock exposed along Bonanza Creek and its tributaries is mostly Cretaceous volcanic and volcaniclastic rock, but Jurassic or Cretaceous siliciclastic rocks are present in its headwaters. Cretaceous or Tertiary dikes or small intrusive bodies are locally present. This area is about 2 miles east of Gold Hill, where the Chisana pluton intrudes Cretaceous volcanic and volcaniclastic rocks. This placer is one of several developed within or peripheral to the pluton (Richter and Jones, 1973; Richter and others, 1975).