Optical mineralogy

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Optical mineralogy is the study of minerals and rocks by measuring their optical properties. Most commonly, rock and mineral samples are prepared as thin sections or grain mounts for study in the laboratory with a petrographic microscope. Optical mineralogy is used to identify the mineralogical composition of geological materials in order to help reveal their origin and evolution.

Some of the properties and techniques used include:

• Refractive index
• Birefringence
• Michel-Lévy Interference colour chart
• Pleochroism
• Extinction angle
• Conoscopic interference pattern (Interference figure)
• Becke line test
• Optical relief
• Sign of elongation (Length fast vs. length slow)^[1]
• Wave plate