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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 ...
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.
Most commonly, rock and mineral samples are prepared as thin sections or grain mounts for study in the laboratory with a petrographic microscope. Optical mineralogy is used to identify the mineralogical composition of geological materials in order to help reveal their origin and evolution. Some of the properties and techniques used include:
In optical mineralogy and petrography, a thin section (or petrographic thin section) is a thin slice of a rock or mineral sample, prepared in a laboratory, for use with a polarizing petrographic microscope, electron microscope and electron microprobe. A thin sliver of rock is cut from the sample with a diamond saw and ground optically flat.
Optical properties of common minerals Name Crystal system Indicatrix Optical sign Birefringence Color in plain polars Anorthite: Triclinic: Biaxial (-) 0.013
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.
Undulose extinction or undulatory extinction is a geological term referring to the type of extinction that occurs in certain minerals when examined in thin section under cross polarized light. As the microscope stage is rotated, individual mineral grains appear black when the polarization due to the mineral prevents any light from passing through.
Mineral tests are simple physical and chemical methods of testing samples, which can help to identify the mineral type. [1] This approach is used widely in mineralogy , ore geology and general geological mapping.