Pumpellyite-(Mg) var. Chlorastrolite (Univ. of Delaware)

Item Description

Chlorastrolite is a rare variety of Pumpellyite-(Mg), a rare very complex Ca-Mg-Al silicate. Both species have their Type Locality in Keweenaw County of Michigan's famed Copper Country. Chlorastrolite is from Isle Royale in Lake Superior. The nickname is green star stone. The polished nodules reveal the striking typical chatoyancy, which generally exhibits a distinctive and attractive mosaic or segmented pattern, sometimes referred to as "turtleback". It is the State gemstone of Michigan (MINDAT). The two polished nodules have the fantastic "turtleback" segmented pattern. Undoubtedly old-time material, but no proof. The rounded flattened nodules were probably found on Isle Royale beaches. Ex University of Delaware Mineralogical Musem. RARE, seldom on the market old-time material. A fine 3-piece collection.