These rocks are Kona Dolomite. Dolomite is a common mineral worldwide; however, Kona Dolomite is only found in one location on the planet which is a hill located in southern Marquette County in Michigan. Normally Dolomite is white, but Kona Dolomite is pink due to pigmentation from the iron in the surrounding rock.
If you take a close look at the photos you will see dark bands embedded in the stone. These are stromatolite (blue-green algae) fossils which are are between 2.1 and 2.2 billion (with a B!) years old from the Middle Precambrian Period.
For me the mind blowing bit is that if any single one of those algae had not grown to the stage where it could pro-create, all life on Earth would not be as it is now. Some species – maybe even humans – would not exist, had the organisms that created these fossils not lived.
Say hello to your four hundred trillionth great grandmother.
