This great formation is found all along the southern edge of Lake Superior, with its type location at Jacobsville 12 miles SSE of Houghton. The formation is a channel filled redbed sandstone which is the yungest of several sedimentary units (Copper Harbor, Nonesuch, Freda, Jacobsville) which represent rift filling units which filled up the gaping Keweenaw Rift Basin.

The boulder at this site, on the grounds of the Carnegie Museum of the Keweenaw came from a quarry near Onkala’s corners about 7 miles SW of Houghton.  The boulder shows the typical red and white Jacobsville colors, which result from groundwater flow and oxidation of tiny magnetite grains in the sandstone and reduction spots that possibly result from organic material in the sandstone.

Overall the Keweenaw Peninsula is underlain by Jacobsville all along its eastern coast. The formation is a generous aquifer and has been quarried extensively as a building stone.