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Bird's Eye Maple (mineral Property)
Bird's eye extinction, or bird's eye maple, is a specific type of extinction exhibited by minerals of the mica group Retrieved 2015-07-02 under cross polarized light of the . It gives the a pebbly appearance as it passes into extinction. This is caused when the grinding tools used to create [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extinction (optical Mineralogy)
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 extinction). Anisotropic minerals specifically will show one extinction for each 90 degrees of stage rotation. The extinction angle is the measure between the cleavage direction or habit of a mineral and the extinction. To find this, simply line up the cleavage lines/long direction with one of the crosshairs in the microscope, and turn the mineral until the extinction occurs. The number of degrees the stage was rotated is the extinction angle, between 0-89 degrees. 90 degrees would be considered zero degrees, and is known as parallel extinction. Inclined extinction is a measured angle between 1-89 degrees. Minerals with two cleavages ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
