That's one I was looking at also, kimberlite. I can't help but notice how much it resembles a chondrite meteorite too. How cool would that be lol!?!? It's strongly magnetic too and I haven't tested density yet but it is heavy for its size. Idk......
Also, I stand corrected on where it came from. It wasnt found in the U.P. It was found in Northern Indiana in a pile of field rocks on my boyfriend's family farm just a few years ago.