Sunday, 23 December 2018

Michigan's state gem : Chlorastrolite

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.