Gold was mined from quartz veins found in the black graphite slate. The Sumdum Mine is located 2.5 miles south of Sanford Cove. Two ledges constitute the Sumdum Chief and Bald Eagle Mines and "have been mined to a depth of several hundred feet below their surface outcrops." Supporting structures included a 10-stamp mill, 4 large Frue Vanners, 2 Pelton wheels, a wagon road, a short tramway, and a wharf.
- United States. Census Office (1893). Report on the Population and Resources of Alaska at the 11th Census, 1890 (Public domain ed.). U.S. Government Printing Office. pp. 47–. Retrieved 6 February 2013.
- Arthur C. Spencer (1906). The Juneau Gold Belt, Alaska, USGS Bulletin No. 287. United States Government Printing Office. pp. 43–45.