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SiO2
Crystal system: Trigonal
Refractive index: 1.544-1.553
Birefringence: 0.009
Cleavage: none
Twinning: none visible
Colour in PPL: colourless
Pleochroism: none
Relief: low
Distinction: readily distinguished by lack of colour, cleavage and visible twinning, low relief and weak birefringence
Occurrence: common mineral
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Polycrystalline Quartz - cross polarised light - Granite petrofabric, Belize
2mm field of view
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