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Almandine (Garnet)
Garnet group - Mesosilicates
Formule chimique :
Fe3Al2(SiO4)3
Système cristallin :
Cubic
Etymologie :
From Alabanda in Asia Minor which must have been an ancient garnet cutting centre.
Dureté :
7 – 7.5
Densité :
4.1 – 4.3
Propriétés physiques :
Glassy sheen. Colour dark red to violet red, may be brownish. Transparent to translucent. Irregular to conchoidal fracture.
Propriétés chimiques :
Insoluble in acids
Formule chimique :
Fe3Al2(SiO4)3
Habitus :
Often in dodecahedral rhomboidal crystals.
Gîtologie :
Almandine garnet is found in metamorphic rocks such as micaschists, gneisses, blue schists and eclogites.
Determination :
difficult to differentiate from other garnet varieties.
Utilisation :
Because of its hardness, garnet can be used as an abrasive. When it is of gem quality, it can be used in jewellery.
Almandine belongs to the garnet family of which it is the iron pole and forms a continuous series with pyrope (magnesium pole). Most of the world’s gemmy garnets come from India or Ceylon. Beautiful specimens also come from Wrangell (Alaska) and Emerald Creek (Idaho).
In France, almandine garnet is found in the granulites of the Massif Armoricain and in the Var.
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