This site represents black sand beach placer deposits tested by the U.S. Bureau of Mines in 1969 (Kimball, 1972). The beach consists of silt to large boulder-sized detritus. The coarser material is mostly of igneous origin, and is thought to have been transported from the Aleutian Range. The finer material consists mostly of quartz and feldspar.

Black sand occurs as a veneer, generally forming thin layers or lenses, that covers wide sections of the upper part of the beach. These layers or lenses rarely exceed 6 inches thick, but one layer measured 14 inches. Buried layers were generally of the same thickness. Some of the black sand lenses are up to a 100 feet long, but most are short and narrow, and rarely cover an acre. A magnetic survey failed to detect any large buried bodies of black sand. Magnetite and ilmenite are abundant in the black sands, however hypersthene is the dominant mineral.