Unfortunately I won't be a great help on your question. Extension, as a part of the College of Ag and Natural Resources doesn't have much expertise in rocks and fossils.
That said, I reached out to our UW Geology Museum. Based on the pictures provided they think it's a rock (rather than a fossil), but they couldn't say much else from the photos provided. They welcome a follow up directly with them at email@example.com
They also suggested that more photos might be helpful and offered a few tips. Take pictures in good light with a neutral backdrop and get plenty of different angles. It's also great if you can include a ruler or coin for scale.
Sorry Extension couldn't be of more immediate help, but hopefully the Geology Museum can get you a more specific ID.
Communications & Technology Manager