Sanidine
Feldspar group
Formule chimique :
(K,Na)AlSi3O8
Système cristallin :
Monoclinic
Etymologie :
from the Greek word sanidion, which means tablet due to the tablet-like shape of sanidine crystals
Dureté :
6
Densité :
2.6
Propriétés physiques :
the luster is vitreous, the colour ranges from white to grey. Translucent to transparent, conchoidal to uneven fracture, good cleavage according to (001)
Propriétés chimiques :
only attacked by hydrofluoric acid.
Formule chimique :
(K,Na)AlSi3O8
Habitus :
often flattened tablet according to (010) or elongated according to (100). Frequent macing (abutment or interpenetration (Carlsbad macing)).
Gîtologie :
Sanidine is a potassium feldspar always associated with magmatic rocks of the alkaline series as for example in rhyolites, trachytes and trachy-andesite.
Determination :
not easy to determine except when macles are clearly visible.
Utilisation :
No major use recognised
Sanidine is a common mineral in the world from the moment alkaline volcanic rocks are found. Many countries have it. In France, sanidine is identified in the Puy-de-Dôme and in the Monts Dore where sanidines often present very beautiful Carlsbad macles (macle by interpenetration of two crystals)
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