FACTOID # 21: 15% of Army recruits from South Dakota are Native American, which is roughly the same percentage for female Army recruits in the state.
 
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Encyclopedia > Pleochroism

Pleochroism is an optical phenomenon in which grains of a rock appear to be different colors when observed at different angles,under a petrographic microscope. Image File history File links Information. ... An optical phenomenon is any observable event which results from the interaction of light and matter. ...


Pleochorism is caused by the double refraction of light by a colored gem or crystal. Light of different polarizations is bent different amounts by the crystal, and therefore follows different paths through the crystal. The components of a divided light beam follow different paths within the stone and travel at different speeds, and each path will absorb different colors of light. When the stone is observed at some angle, light following some combination of paths and polarizations will be present, each of which will have had light of different colors absorbed. At another angle, the light passing through the stone will be composed of another combination of light paths and polarizations, each with their own color. The light passing through the stone will therefore have different colors when it is viewed from different angles, making the stone seem to be of different colors. A calcite crystal laid upon a paper with some letters showing the double refraction Birefringence, or double refraction, is the division of a ray of light into two rays (the ordinary ray and the extraordinary ray) when it passes through certain types of material, such as calcite crystals, depending on... This article does not cite any references or sources. ... A selection of gemstone pebbles made by tumbling rough rock with abrasive grit, in a rotating drum. ... Quartz crystal Synthetic bismuth hopper crystal Insulin crystals Gallium, a metal that easily forms large single crystals A huge monocrystal of potassium dihydrogen phosphate grown from solution by Saint-Gobain for the megajoule laser of CEA. In chemistry and mineralogy, a crystal is a solid in which the constituent atoms... This article treats polarization in electrodynamics. ...


Some stones show two colors or shades and are called dichroic. Some show three and are trichroic. Gems are sometimes cut and set either to display pleochroism or to hide it, depending on the colors and their attractiveness. In optics, the term dichroic has two related but distinct meanings. ...


Pleochroism is an extremely useful tool in mineralogy for mineral identification, since minerals that are otherwise very similar often have very different pleochroic color schemes. In such cases, a thin section of the mineral is used and examined under transmitted light in a microscope. Mineralogy is an earth science that involves the chemistry, crystal structure, and physical (including optical) properties of minerals. ... A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure and specific physical properties. ... Robert Hookes microscope (1665) - an engineered device used to study living systems. ...


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  Results from FactBites:
 
Pleochroism - Wikipedia, the free encyclopedia (187 words)
Pleochroism is an optical phenomenon where due to double refraction of light by a colored gem or crystal, the light is divided into two paths which are polarized at a 90° angle to each other.
Gems are sometimes cut and set either to display pleochroism or to hide it, depending on the colors and their attractiveness.
Pleochroism is an extremely useful tool in mineralogy for mineral identification, since minerals that are otherwise very similar often have very different pleochroic color schemes.
Mineral Gallery - Pleochroism, Phosphorescence and other light effects (1012 words)
Pleochroic minerals are minerals that show different colors depending on what direction the viewer is observing the crystal.
Many minerals are technically pleochroic, but more often than not the color change is so small that it requires optical instruments to detect it.
Pleochroism is caused by the absorption of different wavelengths of light travelling through different directions in the crystal.
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