Image: <bdi><a href="https://www.wikidata.org/wiki/Q126871365" class="extiw" title="d:Q126871365"><span title="photographer from the United States">Shannon Heinle</span></a></bdi> (CC0)
orthorhombicuncommonSilicates
Cordierite
Mg2Al4Si5O18
This sample of Cordierite displays an unusual blue-violet color, often compared to a light blue sapphire with a purplish tint. It is strongly pleochroic, meaning it shows different colors when viewed from different angles, and the sample is approximately 7 cm in size.
Cordierite Physical Properties
Mohs Hardness
7Crystal System
orthorhombicLuster
vitreousStreak Color
whiteCleavage
distinct on {010}, poor on {100} and {001}Fracture
conchoidal to unevenSpecific Gravity
2.65Colors
blue-violet, light blue, purplishTransparency
transparent to translucentType Locality
OntarioMineral Group
SilicatesUses
jewelry, collectorAssociated Minerals
Rarity
uncommonGeological Context
Cordierite typically forms in metamorphic rocks such as gneiss, schist, and hornfels, resulting from the regional or contact metamorphism of argillaceous (clay-rich) sediments. It can also occur in some igneous rocks.
