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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 ...
Optical properties of common minerals Name Crystal system Indicatrix Optical sign Birefringence Color in plain polars Anorthite: Triclinic: Biaxial (-) 0.013: None Biotite: Monoclinic: Biaxial (-) 0.045: Brown Calcite: Hexagonal: Uniaxial (-) 1.486: None Chlorite: Monoclinic triclinic: Biaxial (-) or (+) 0.011: Pale green Cinnabar: Trigonal ...
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.
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
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.
Staurolite is a reddish brown to black, mostly opaque, nesosilicate mineral with a white streak. It crystallizes in the monoclinic crystal system, has a Mohs hardness of 7 to 7.5 and the chemical formula: Fe 2+ 2 Al 9 O 6 (SiO 4) 4 (O,OH) 2. Magnesium, zinc and manganese substitute in the iron site and trivalent iron can substitute for aluminium.
Pleochroism is an extremely useful tool in mineralogy and gemology for mineral and gem identification, since the number of colors visible from different angles can identify the possible crystalline structure of a gemstone or mineral and therefore help to classify it. Minerals that are otherwise very similar often have very different pleochroic ...
Braggite is a sulfide mineral of platinum, palladium and nickel with chemical formula: (Pt, Pd, Ni)S. It is a dense (specific gravity of 10), steel grey, opaque mineral which crystallizes in the tetragonal crystal system. [3] It is the central member in the platinum group end-members cooperite and vysotskite.