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Color index, as a geological term, is a measure of the ratio between generally dark mafic minerals and generally light felsic minerals in an igneous rock. [ 1 ] [ 2 ] The color index of an igneous rock is the volume percentage of mafic minerals in the rock, excluding minerals generally regarded as "colorless" such as apatite , muscovite ...
In astronomy, the color index is a simple numerical expression that determines the color of an object, which in the case of a star gives its temperature. The lower the color index, the more blue (or hotter) the object is. Conversely, the larger the color index, the more red (or cooler) the object is.
Pages in category "Geology" The following 62 pages are in this category, out of 62 total. ... Collage (geology) Color index (geology) Compatibility (geochemistry)
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: Refractive index; Birefringence; Michel-Lévy Interference colour chart; Pleochroism; Extinction angle; Conoscopic interference pattern (Interference ...
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.
Geology portal; Earth sciences portal; List of minerals – List of minerals with Wikipedia articles; List of rocks on Mars – Alphabetical list of named rocks and meteorites found on Mars; Rock cycle – Transitional concept of geologic time; List of rock formations: for a list of unusual or culturally significant rock outcrops
Color index, or the modal abundance of minerals other than quartz, plagioclase and alkali feldspar (e.g., mafic silicates, oxides, sulfides, phosphates, etc.), can be used to infer the maturity of a granite. Juvenile I-type granites have a higher color index. Amphibole, biotite, sphene, allanite, and oxides are typically more abundant. In ...
The color index of S-type granites can vary from melanocratic to leucocratic. Higher color indices correlate with higher plagioclase to alkali feldspar ratios. [7] The most common high color index mineral in an S-type granite is biotite. [1] [4] Figure 7.