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Click Here For Best Selection Of High Quality Polarizing Microscope

Click Here For Best Selection Of High Quality Polarizing Microscope

In optical mineralogy, it is greatly understood that the interference figures are always symmetrical in shape and distribution of color to the planes and axes of symmetry of the crystal system. They are most symmetrical in orthorhombic, less so in monoclinic, and still less in triclinic crystal system.

 

            The figures found exhibited by the orthorhombic crystals under petrographic polarizing microscope are always in two of the pinacoids and in white light the color distribution will be symmetrical to the trace of the axial plane and the line through the center at right angles to this trace as well as to the central point.

 

            The figures like the clinopinacoid are usually shown by the monoclinic crystals or in sections at right angles to this. The color distribution is never symmetrical to two lines in white light of polarizing microscope for mineralogists. But then it is symmetrical either to the trace of the axial plane or to the line through the center at right angles to this trace, or to the central point.

 

            In white light, the figures shown by triclinic crystals have distribution of color unsymmetrical to any line or point. The color fringes of the hyperbola in white light are usually due to the dispersion of the optic axes and bisectrices. There is a particular interference figure for each color. The color fringes are usually produced by the overlapping of these superposed figures.

 

            It should be noted that the color with the larger axial angle is nearer to the center of the field. This is commonly due to the extinguishing of light of each color at the axial points. That is, the resulting colors at this points that are produced by white light minus the absorbed color. The dispersion of the optic axes can be determined by measuring the axial angle in red and blue light.



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Monday, April 28th, 2008 at 3:30 am
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Optical Mineralogy
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Click Here For Best Selection Of High Quality Polarizing Microscope