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Click Here For Best Selection Of High Quality Polarizing Microscope

Click Here For Best Selection Of High Quality Polarizing Microscope

Certain minerals, otherwise colorless in thin section, show curious circular brown areas when viewed in polarized light of the petrographic polarizing microscope. Each of which contains at its center an included fragment of some other mineral. These brown patches change color when the section is rotated above the polarizer of the polarizing microscopes. They are in fact, pleochroic areas in an otherwise colorless section. It is quite certain that the including mineral has acquired this property in consequence of the presence of this minute inclusion that is more clearly exhibited when the section is evaluated with the aid of the petrographic polarizing microscope. Several theories have been put forward to account for these pleochroic haloes, but it has bees satisfactorily proved that the development color around the inclusion is the result of the fact that such an inclusion is radioactive, and that its ejected particles have produced an ionization effect on the mineral in contact. Minerals showing these haloes when viewed under geological polarizing microscope are muscovite, cordierite, tourmaline, and biotite. The last two minerals are not colorless, even in thin section, but in their case the color has been rendered more intense around the inclusion and it can be clearly noticed when they are examined under polarized light microscopes.  



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Wednesday, February 13th, 2008 at 3:47 am
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Characters of Minerals in Polarized Light
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Click Here For Best Selection Of High Quality Polarizing Microscope