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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 ...
With a known thickness of the thin section, minerals have specific and predictable colours in cross-polarized light, and this chart can help identify minerals. The colours are produced by the difference in speed in the fast and slow rays, also known as birefringence.
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.
In many colored minerals such as biotite, hornblende, tourmaline, chlorite, these two rays have different colors, and when a section containing any of these minerals is rotated the change of color is often clearly noticeable. This property, known as "pleochroism" is of great value in the determination of mineral composition.
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
Optical properties of common minerals Name Crystal system Indicatrix Optical sign Birefringence Color in plain polars Anorthite: Triclinic: Biaxial (-) 0.013
Download as PDF; Printable version; ... Opaque, transparent in thin fragments: Density: 5.6 – 5.8, Average = 5.69 ... Samarskite is a radioactive rare earth mineral ...
Optical relief (usually noted as simply relief) is a visually observable property in optical mineralogy used to identify minerals based on their refractive index.Relief is determined by observing the degree to which grains stand out from a mounting medium of known refractive index, [1] usually either oil or Canada Balsam.