ISLE ROYAL GREENSTONE
Isle Royal Greenstone
Michigan's State Gemstone
Chlorastrolite is a variety of the mineral Pumpellyite, related to prehnite and Thomsonite. It is composed of finely radiated or stellated masses, some containing copper or silver. Found in the Keweenaw Peninsula and on Isle Royal (not permitted to take off the island). First recorded findings in 1847 and became Michigan’s official State Gem Stone in 1972.
Good quality Greenstones are considered semi-precious gems of rare beauty, sometimes called Turtle Back stones.