Michigan’s state gem is a green, turtle-backed mosaic that forms in the gas cavities of the billion-year-old lavas here, and the finest come from Isle Royale. Be clear before you go: Isle Royale is a national park and collecting greenstone there is PROHIBITED, full stop. The legal way to hold one is to hunt the Keweenaw beaches and mine dumps on the mainland where access is permitted, or buy a cut stone from a Copper Country lapidary.
Chlorastrolite
See it on the map
Other places on the map within a couple of hours.
