I found this along the Fox River in Elgin, IL. At first I thought it was a stromatoporoid fossil (I find them everywhere in this area), but upon closer inspection I couldn't see anything that looked like pillars or laminae. Someone suggested chaetetid sponge, or a stromatoporoid that was distorted by silicification. I can't find any photos that look like my spec. except dino bone and we don't have those in northern Illinois. Is it a natural formation, crazy looking oolites? I'm totally stumped!
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