Hi! I'm new here, so PLEASE forgive me any infractions.
On an annual trip to Ann Arbor, Michigan, I took a day trip to South Haven, Michigan (more specifically Deer Lick Creek Park, on the west coast, above St Joseph). I found a rock with an interesting inclusion. Deer Lick Creek empties into Lake Michigan. After some research, the bedrock in that area is Shale. (I don't know if that helps).
So...a rock, possibly a septarian nodule, found at Deer Lick Creek beach, which is near South Haven, Mi, bedrock is shale.
Attached is a picture of the rock in question.