extinction angle
Quick Summary
The extinction angle is a concept in optical crystallography, which is the study of the optical properties of crystals. It refers to the angle through which a crystal is rotated from a specific line, such as a crystallographic axis, to the plane where maximum extinction occurs.12
Optical crystallography is important for identifying minerals, especially when their external crystalline form is not visible, such as in thin sections of rocks viewed under a microscope. Crystals are classified based on how they interact with polarized light, leading to categories like optically isotropic, uniaxial, and biaxial crystals. Some minerals also exhibit fluorescence, emitting visible light when exposed to ultraviolet radiation.23
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