Chlorastrolite is Michigan's official state gemstone and is known locally as "Isle Royale Greenstone". Scientifically, they are a form of the mineral pumpellyite. Available analyses suggest the Michigan pumpellyites are magnesium-dominant, intermediate solid solution series between pumpellyite (Mg+), pumpellyite (Fe2+) and pumpellyite (Fe3+). (Robinson, 2004). FOV is approx. 6 cm. wide, with the main greenstone nodule about 2 cm. across. This specimen was collected in July, 2007.
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