Show Summary Details

Quick Reference

An important alkali amphibole of composition Na2(Mg3Al2)[Si8O22](OH)2, and end-member of the glaucophane–riebeckite (Na2(Fe2+3Fe3+2)[Si8O22](OH)2 series; sp. gr. 3.0; hardness 6.0; blue, bluish-black; prismatic crystals, fibrous or granular habit; it is an essential mineral of blueschists under conditions of low temperature and high pressure in metamorphosed sediments at destructive plate margins.

Subjects: Earth Sciences and Geography.

Reference entries

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.