 Extinction (optical mineralogy)

In optical mineralogy, "extinction" refers to the phenomenon observed when a polarized light beam interacts with a mineral grain in a thin section under a microscope. It describes the behavior of light as it passes through a mineral when it is aligned in certain orientations relative to the polarizers. When observing a mineral under crossed polarizers, extinction occurs when the mineral is oriented in such a way that no light is transmitted through the mineral.