Better refractometer results with the Bright Line technique

[Barbra Voltaire, FGG]

Abstract: Grazing incidence illumination of gemstones on the gemmologist’s refractometer is now little used, but offers some significant advantages. The authors review the history of such use, give detailed explanations of how it is accomplished, and provide suggestions for its application to practical problems. There are three principal applications of grazing incidence illumination that can aid the gemmologist in practical discrimination between gems. One is in easier and better determination of the refractive index, or indices for birefringent stones. The second is in estimation of relative dispersion, and the third is in being able to observe polarized absorption spectra of gems.

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