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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 .
Thin sections are prepared in order to investigate the optical properties of the minerals in the rock. This work is a part of petrology and helps to reveal the origin and evolution of the parent rock. A photograph of a rock in thin section is often referred to as a photomicrograph.
Michel-Lévy interference colour chart issued by Zeiss Microscopy. In optical mineralogy, an interference colour chart, also known as the Michel-Levy chart, is a tool first developed by Auguste Michel-Lévy to identify minerals in thin section using a petrographic microscope.
Optical properties of common minerals Name Crystal system Indicatrix Optical sign Birefringence Color in plain polars Anorthite: Triclinic: Biaxial (-) 0.013
In optical mineralogy, a petrographic microscope and cross-polarised light are often used to view the interference pattern. The thin section containing the mineral to be investigated is placed on the microscope stage, above one linear polariser, but with a second (the "analyser") between the objective lens and the eyepiece.
Colour of minerals in crossed polarized light (XPL), particularly notable in thin section. See also optical mineralogy. Twinning; Crystal twinning present and type. Extinction angle; Degrees which mineral turns black in XPL in microscope. Zoning; Mineral zoning present. Mineral texture
Extinction is a term used in optical mineralogy and petrology, which describes when cross-polarized light dims, as viewed through a thin section of a mineral in a petrographic microscope. Isotropic minerals, opaque (metallic) minerals, and amorphous materials (glass) do not allow light transmission under cross-polarized light (i.e. constant ...
Photomicrograph of a thin section of gabbro in cross-polarized light. A petrographic microscope is a type of optical microscope used to identify rocks and minerals in thin sections. The microscope is used in optical mineralogy and petrography, a branch of petrology which focuses on detailed descriptions of rocks