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Glaucophane
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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