Itrongay (Itrongahy), Mahasoa Est, Betroka, Anosy, Madagascar

KAlSi₃O₈

Crystal System: monoclinic
Colour: colourless, white, grey, yellowish white or reddish white
Lustre: vitreous
Habitus: tabular crystals on {010}, with square cross section. Carlsbad twins are common; twinning according to Manebach and Baveno laws are rarer
Hardness: 6
Fracture: irregular/uneven, conchoidal
Cleavage:  perfect on {001}, distinct on {010}
Density: 2.56 g/cm³ 
Origin and geological occurrence: it is a common mineral in sialic volcanic rocks of high temperature.

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Samples:

9F.21 Sanidine Prismatic phenocrysts in lava #tectosilicates

	9F.7 Sanidine Twinned crystals according to Carlsbad law. Samotracia Island, Greece. #tectosilicates
	9F.8 Sanidine Phenocrysts in rhyolite. #tectosilicates