Ampanihy, Atsimo-Andrefana, Madagascar

(Ca,Na)[Al(Al,Si)Si₂O₈]

Crystal System: triclinic
Colour: pale green, blue, colourless, grey-white
Lustre: vitreous; pearly on cleavage surfaces.
Habitus: usually as cleavable, granular or massive aggregates formed by tabular crystals. Twinning is common.
Cleavage: perfect {001}, less perfect on {010}. Distinct on {110}.
Fracture: uneven to conchoidal.
Density: 2.685-2.710 g/cm³
Origin and geological occurrence: “labradorite” is a member of the plagioclase series, with composition ranging between An₅₀ to An₇₀. It occurs in mafic igneous rocks and in anorthosite. It is rarer in metamorphic rocks (e.g., amphibolite). It may be a detrital mineral in sedimentary rocks.

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Samples:

9F.19 Labradorite Cleavable mass with black pyroxene. #tectosilicates