Optical mineralogy

right|thumb|A calcite crystal laid upon a graph paper with blue lines showing the double refraction right|thumb|In this example, optic axis along the surface is shown perpendicular to plane of incidence. Incoming light in the polarization (which means perpendicular to plane of incidence – and so in this example becomes "parallel polarisation" to optic axis, thus is called extraordinary ray) sees a greater refractive index than light in the polarization (which becomes ordinary ray because "perpendicular polarisation" to optic axis) and so polarization ray is undergoing greater refraction on ent

Petrography is a branch of petrology that focuses on detailed descriptions of rocks. Someone who studies petrography is called a petrographer. The mineral content and the textural relationships within the rock are described in detail. The classification of rocks is based on the information acquired during the petrographic analysis. Petrographic descriptions start with the field notes at the outcrop and include macroscopic description of hand-sized specimens. The most important petrographer's tool is the petrographic microscope. The detailed analysis of minerals by optical mineralogy in thin se

thumb|Pleochroism of cordierite shown by rotating a polarizing filter on the lens of the camera thumb|Pleochroism of tourmaline shown by rotating a polarizing filter on the lens of the camera

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optical microscope

laboratory preparation rock, mineral, soil, pottery, bones, metal for petrographic microscope

birefringence-free direction of light transmission

The optical properties of rocks and minerals

A pattern of birefringence colors

geological term

aspect of crystal optics

term used in optical mineralogy and petrology