Staurolite

The staurolite (or staurolite) also called " hone croix" minéral of the family of the Nésosilicate S. Its chemical formula is a is and crystallizes in the crystalline Système monoclinical.

She appears herself as a brown prism, very often twinned in cross. The macle with 60º (“cross of Saint Andre”) is more frequent than the macle with 90º (“Greek cross”). Indeed, its name comes from the Greek stauros , cross.

3 types of Staurolites, source: Brittany, France.

Layer

Staurolite often meets in the Micaschiste S or the Gneiss and gives an interval of pressure temperature and the degrees of metamorphism.

• Crystals of 20 cm to Scaër and Coray in the Finistere, like with Baud and Locminé in the Morbihan, in France

• twinned Cristaux coils of it (3 interpenetrated crystals with 60°) known with Fanin and Cherokee in Georgia with the the United States
• Cristaux not twinned with Monte Campione and Pizzo Forno in the Saint-Gothard in Suisse

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