Chlorastrolite (original) (raw)

Chlorastrolite, also known as Isle Royale Greenstone, is a green or bluish green stone. Chlorastrolite has finely radiating or stellate (for examples, see crystal habits) masses that have a "turtleback" pattern. The stellate masses tend to be chatoyant, meaning they have a varying luster. This chatoyancy can be subtranslucent to opaque. Cholorastrolite is a variety of pumpellyite: Ca2(Mg,Fe)Al2(SiO4)(Si2O7)•(OH)2H2O. Chlorastrolite was once thought to be an impure variety of prehnite or thomsonite.