2. BASIC COMPONENTS. Coarse mineral components.
Only Polarizer. Colorless, dirty (due to alterations), with not very clear perpendicular exfoliations, low relief, sometimes with prismatic habits.
Polarizer and Analyzer. Gray interference colors.
Potasic Feldspars. Orthoclase: similar to quartz but dirty in appearance (or grayish), in some occasions with twins formed by two crystals. Microcline: with repeated twins.
Calcium-Sodium Feldspars. Plagioclases: with laminar polysynthetic
twins.
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