Pg. 27, 30 (table 1), 32. Hardwood gneiss. Dark medium-grained gneiss composed of hornblende, plagioclase, and pyroxene, which is interlayered with dark fine-grained gneiss, beds of light-colored gneiss with light and dark laminae, garnet-quartz-mica schist, and light-colored rock that resembles quartzite but is probably volcanic in origin. Layers are a fraction of an inch to a few feet in thickness; layering in general dips easterly at angles less than 40 deg. Known thickness, including metagabbro sills, possibly no more than several hundred feet. Separated by covered interval from strata of Dickinson group (new); may be in part or wholly equivalent to group but exposures are inadequate to establish relationship. Age is early Precambrian (pre-Animikie). Report includes stratigraphic sequence chart.
Exposures just west of town of Hardwood, in secs. 5 and 8, T. 41 N., R. 27 W., Dickinson Co., Northern Peninsula, northwestern MI (Lake Superior region). Named from town of Hardwood. Also, excellent exposures along and adjacent to Highway M69. Author considers unit to be highly distinctive, containing rocks not known elsewhere in northern MI.

Source: US geologic names lexicon (USGS Bull. 1200, p. 1674); supplemental information from GNU records (USGS DDS-6; Reston GNULEX).