Northern Canada is home to several large diamond deposits, and glaciers snuck some south to Michigan. The coral that formed Petoskey stones (Hexagonaria percarinata) went extinct before dinosaurs were even born. © 2020 Advance Local Media LLC. Abram said he knows why the story took off online. Diamonds are found within a 200-mile swath that runs from Iowa to Ohio. While she’s not a big rock collector herself, she does have some tips for people wanting to add to their collections: “My advice to anybody that is interested in collecting rocks is to always look down. He based the report mostly on a YouTube video he saw. Rockhounds, check out “Lake Michigan Rock Picker’s Guide,” “Lake Superior Rock Picker’s Guide” and “Lake Huron Rock Picker’s Guide” co-authored by Kevin Gauthier and Bruce Mueller for more information about our state’s coolest stones. So for a brief moment online, Abram's big rock was all the rage. But it’s more common to see them at popular beaches, because most of the Petoskeys have already been picked up. Photo courtesy of the state of Michigan.