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Fluorite or Calcium Fluoride in a 'perfect' single crystal has a cubic arrangement of the atoms so it is isotropic (very low birefringence). Unlike any glasses that have impurities and density inhomogenaeities no matter how carefully made, it has very little scattering effect on light. It also has the property of low dispersion. That is variation of refractive index to wavelength.
It is so unlike any glass with inherent impurities and inhomogenaeities. This is why the laser beam disappears.
Bert
Last edited by avandonk; 08-01-2009 at 02:53 PM.
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