Rio Oremo, Chiavolino, Pollone, Biella Province, Piedmont, Italy

Na₂Mg₃Al₂Si₈O₂₂(OH)₂

Crystal System: monoclinic
Colour: grey to lavender-blue
Lustre: vitreous
Habitus: prismatic
Hardness: 5 - 6
Fracture: conchoidal or uneven
Cleavage: perfect on {110}
Density: 3.132 g/cm³ (calc)
Origin and geological occurrence: glaucophane is characteristic of the blueschist facies, in former subduction zones in mountain belts; in the greenschist facies and in eclogites that have undergone retrograde metamorphism.

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Samples:

9D.7 Glaucophane Aggregate of deep blue acicular crystals.  #inosilicates