Also known as “Isle Royale Greenstone”, “Michigan Greenstone”, and “Green Starstone,” chlorastrolite is easily identified by its “turtleback” pattern and its rich blackish-green color. A variety of the mineral pumpellyite, its distinct green color is caused by the inclusion of chromium, iron, and other trace elements in its composition.  

Chlorastrolite is only found in the Lake Superior region of North America. Volcanic, glacial, and metamorphic activity in the region is responsible for the formation of this distinctive mineral. Sculpted into cabochons, carved objects, or polished in its natural state, Chlorastrolite is popular with lapidarists and specimen collectors alike.