Epidote group - Sorosilicate

Formule chimique : Ca2FeAl2(Si2O7)(SiO4)(O,OH)2
Système cristallin : Monoclinic
Etymologie : From the Greek Epidosis which means "complement".
Dureté : 6
Densité : 3.4
Propriétés physiques : Transparent to opaque, usually translucent. Colour Grey, green to black, rarely colourless. Glossy to resinous sheen. Perfect basal cleavage (001). White trace.
Propriétés chimiques : Only soluble in hydrofluoric acid.
Formule chimique : Ca2FeAl2(Si2O7)(SiO4)(O,OH)2
Habitus : Often in elongated prismatic crystals. Sometimes acicular, or in fibrous or granular masses.
Gîtologie : Epidote is a mineral of calcic metamorphic rocks, cipolins and skarns (contact metamorphism in limestone).
Determination : difficult
Utilisation : When it is of gem quality, epidote can be used in jewellery.

Epidote forms a continuous series with clinozoisite and piémontite.
The main deposits of beautiful epidotes are located in Austria (Zillertal, Knappenwand), Pakistan (Skardu), Finland (Outokumpu) and Germany (Erbendorf).
In France, epidote can be found in the Dauphiné, on the Ile de Groix and in the Pyrenees.

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