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(POTASSIC and ALKALI FELDSPARS) Ka[AlSi3O8]
Crystal system: Monoclinic
Refractive index: 1.518-1.534
Birefringence: 0.006-0.007
Cleavage: 1 perfect, 1 good intersecting at right-angles
Twinning: carlsbad
Colour in PPL: colourless
Pleochroism: none
Relief: low
Distinction:
Occurrence: volcanic felsic rocks
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Perthite - Plain polarised light - Faza petrofabric, Yemen - Field of view 1mm
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