Image: <a href="//commons.wikimedia.org/wiki/User:Archaeodontosaurus" title="User:Archaeodontosaurus">Didier Descouens</a> (CC BY-SA 3.0)
orthorhombicuncommonSilicates
Cordierite
(Mg,Fe)2Al4Si5O18
A transparent, faceted gemstone displaying strong pleochroism, shifting between deep blue-violet and yellowish-gray hues depending on the viewing angle.
Cordierite Physical Properties
Mohs Hardness
7Crystal System
orthorhombicLuster
vitreousStreak Color
whiteCleavage
distinct to poor on {010}Fracture
subconchoidal to unevenSpecific Gravity
2.65Colors
blue, violet, yellowish-gray, colorlessTransparency
transparentType Locality
Coimbatore District, Chennai (Madras), Tamil Nadu, IndiaMineral Group
SilicatesUses
jewelry, collectorAssociated Minerals
quartz, feldspar, garnet, sillimanite, biotiteRarity
uncommonGeological Context
Cordierite typically forms in high-grade metamorphic rocks like gneisses and schists, resulting from the alteration of aluminous sediments, and can also be found in some granitic pegmatites.
