petoskey

I found this giant in Lake Michigan today in South Haven, MI area. It seems to be similar to agatized sponges I've found in material, but not in look. I think this ones pretty cool. Haven't cut into it yet...Any ideas what it is?

Best Rockhounding spots in Michigan? Got Any? Here's mine. I'm taking a little trip up the coast of Lake Michigan from Grand Rapids and ending up in the Upper Peninsula west of Marquette a couple hours. I'm looking for suggested stops along the way to rockhound. If you are willing to share...