AN EXPERIMENTAL GEOPHYSICAL APPROACH TO OPTICAL MINERALOGY:

The Faraday effect is a magneto-optical phenomenon that describes the rotation of the plane of polarization of light, within a medium, in the presence of an external magnetic field. It is given by the linear relationship: θ = ν B L. Where θ = rotation, ν = Verdet’s constant, B = magnetic field and L = length of the fluorite crystal. This experiment measures the Verdet’s constant for three different samples of pure fluorite whose different colors are thought to correspond to different minor impurities. The measured values will then be compared to the standardized value for fluorite (Weber, Marvin J. Handbook of Optical Materials. Boca Raton: CRC, 2003. Print). The objective of this experiment was to check whether there exists a relationship between the different colored samples and any deviation in the Verdet’s constant. The experimental setup consists of a laser, a polarizer to transmit plane polarized light, a solenoid to generate a uniform external magnetic field within which the crystal sample is placed, an analyzer, and a pin-hole photodiode. The change in the polarization angle was recorded with respect to the change in the magnetic field. Once the Verdet’s constants were obtained, the samples were powdered and tested for major trace element geochemistry to determine their specific impurities. Further analysis will determine if the impurities in the sample significantly affect the Verdet’s constant or if the Verdet’s constant is independent of the color of the samples.