Gem Identification (Part 3) Polariscopy

This is a gemological instrument called a polariscope. The gemstone is placed between the two lenses and illuminated. Depending upon what is seen through the top lens the OPTICAL CHARACTER of the unknown gemstone can be determined. This is a very important factor as gemstones are either singly refractive (isotrophic) or doubly refractive (anisotrophic). In this case, the unknown red cabochon shows a doubly refractive response.