Amphibole group

Formule chimique : Na2(Mg,Fe2+)3Al2Si8O22(OH)2
Système cristallin : Monoclinic
Etymologie : Glaucophane comes from the Greek Glaukos for its colour
Dureté : 6
Densité : 3.1
Propriétés physiques : Glaucophane has a matt to vitreous sheen and can be slightly pearly. Its colour is generally blue-grey to lavender blue. Its cleavage is perfect.
Propriétés chimiques : Glaucophane is insoluble in acids.
Formule chimique : Na2(Mg,Fe2+)3Al2Si8O22(OH)2
Habitus : In fine prisms or in most cases in clusters. Rarely macerated.
Gîtologie : Glaucophane is characteristic of high pressure, low to medium temperature metamorphic rocks. (Blue shale facies)
Determination : Easy but can be confused with riebeckite
Utilisation : For mineralogical interest. No notable uses.

Glaucophane is a blue amphibole found in high-pressure, low-temperature micaschists. In France, the most famous glaucophane deposits are located on the island of Groix (protected deposit with harvesting ban). Glaucophane is also found in the Alps.

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