Named for exposures near town of Richmond along valley of Sauk River in southwestern Stearns Co, MN in Lake Superior region. Type locality designated for two small, abandoned quarries approximately 3 km east of Richmond in NE1/4 SE1/4 sec 19 of Wakefield Township (T123N, R30W). Other reference localities include outcrops and quarries in SW1/4 and NE1/4 sec 22, and along MN Hwy 23 near western edge of Rockville in NE1/4 sec 17, T123N, R29W. Other exposures near village of Cold Spring in NE1/4 NE1/4, sec 26, Wakefield Township, where quarried under trade name "Cold Spring Pearl Pink Granite" and in 1978 marketed as "Opalescent Gray". Originally mapped as part of Stearns Igneous Complex of Woyski (1949) but is clearly metamorphic, containing vague foliations and localized potassium-feldspar porphyroblasts as much as 10 mm long. Is mostly black to dark grayish black, with local dark-reddish-gray to pale-red zones concentrated along irregularly spaced joints or cataclastic zones where original rock has been oxidized. Has small inclusions of biotite schist and lenticular amphibolite masses. Detailed lithology, geologic map, areal limits given. Is early Precambrian in age.

Source: GNU records (USGS DDS-6; Denver GNULEX).