Chlorastrolite
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: Ca
2(Mg,Fe)Al
2(SiO
4)(Si
2O
7)•(OH)
2H
2O. Chlorastrolite was once thought to be an impure variety of prehnite or thomsonite.
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