Isle Royale greenstone, this state's official gem, is found on Isle Royale in Lake Superior
Here are just a few of the Petoskey stones I have found at the Lake Michigan 
..... Rock, Rocks Gems, Rocks Crystals, Hobby Rockhounding, Superior Rocks... [DOC] [TLE] State Gem: Isle Royale Greenstone - Pinterest [PAR] Isle Royale Greenstone (Chlorastrolite), the state gem of Michigan, is a .....