The Dr. and I traveled 510 this past summer because we were told it contained many neat geologic stops along the way; one of those stops was "Black Rock". Below is a geologic description from the Marquette Fieldtrip Guidebook written by the ILSG for Black Rock and the reason behind its name:
Quote:Stop 10 - BIF, Basalt, Gabbro
This outcrop consists of iron formation in contact to the north and south with massive basalt. To the west the basalt is cut by gabbro. The contact between the basalt and gabbro follows the highway. The iron-formation is approximately 5 feet thick and trends N30°W. It is compcsed almost exclusively of fine, black
chert which contains scattered magnetite grains and abundant pyrite, To the west of this locality, the iron-formation member is generally layered with 1/2 inch chert and magnetite bands. Although the magnetite content can be highly
variable, the iron-formation produces a strong magnetic signature. The basalt is dark green to black, fine-grained and relatively non-foliated. The gabbro is medium-grained, ophitic to sub-ophitic, and is composed of equigranular amphibole, plagioclase and chlorite.