Glaucophane
Image: Andrew Silver (Public domain)
Mineral NameGlaucophane
Chemical FormulaNa₂Mg₃Al₂Si₈O₂₂(OH)₂
Mohs Hardness5
Crystal Systemmonoclinic
Lustervitreous
Streak Colorpale blue to grayish blue
Cleavageperfect on {110}, in two directions at ~56° and ~124°
Fractureuneven
Specific Gravity3.1
Colorsblue, lavender-blue, grayish blue
Transparencytranslucent
Type LocalityCalifornia (USA), Japan, Alps (Europe)
Mineral GroupSilicates (Amphibole Group)
Usescollector, scientific (indicator mineral)
Associated Mineralslawsonite, epidote, garnet, jadeite, chlorite, albite, quartz
Rarityuncommon
Description
The image displays a specimen of glaucophane, exhibiting its characteristic blue color and a somewhat fibrous to prismatic aggregate texture. A pen is included for scale, showing the specimen to be a hand-sized piece.
Geological Context
Glaucophane is a diagnostic mineral of blueschist facies metamorphic rocks, forming under high-pressure, low-temperature conditions typically found in subduction zones. Its presence indicates a specific tectonic environment.
