Refractive Index Of Ruby And Sapphire
The primary use of refractometer is to measure the angle at which light travelling through the gemstone is bent or refracted this measurement is called refractive index(RI). The refractive index of ruby and sapphires are 1.762-1.770, Corundum is uniaxial negative, Gem materials for the most part accord which these values and show birefringence of 0.008. Both ruby and sapphire show distinct pleochroism. Blue sapphire normally shows blue-green to yellow-green in the extraordinary ray and pale to deep blue in the ordinary ray, ruby showing orange-red in the extraordinary ray and bluish red in the ordinary ray. When possible, both rubies and sapphires should be cut with the c-axis at right angles to the table facet, to display the best colour.