|Michigan's state gem is found in one place -- and you won't find it anywhere else. Chlorastrolite is a variety of the mineral pumpellyite, and it is exclusively found along the Keweenaw Peninsula and throughout the Isle Royale archipelago -- Michigan's most remote national park. |
Commonly called Isle Royale Greenstone, ancient lava flows cooled into basalt.
|Within that basalt were small pockets of empty space left behind from gasses in the lava -- and that is where chlorastrolite eventually formed. Chlorastrolite is difficult to find because of its size. Large pieces are extremely rare.|