Optical Microscopy

The optical microscopy of transmitted and reflected light is one of the most used techniques in geological works. It serves for the determination of optical properties, identification of minerals, study of textures and relationships between minerals and the classification of rocks.
The microscope uses polarized light. While unpolarized light is one that vibrates in all directions, polarized light only vibrates in a single plane or direction of vibration. In the microscope, using transmitted light, light vibrates in the N-S direction, perpendicular to its direction of propagation. The beam of polarized light is transmitted from the lower region of the microscope, where the source of illumination is located, and incites perpendicularly on the sample, penetrates in its interior and is transmitted through the minerals, interacting with its internal structure.
After interacting with the internal structure of the mineral, the light leaves the mineral, travels through the tube system of the microscope, until it reaches the observer. It is important to note that as a consequence of the anisotropy that most minerals present, the propagation and interaction of the light beam with the internal structure of the mineral can vary significantly with the crystallographic directions.