One of the biggest challenges for a gemologist is not only obtaining accurate data for a particular gem, but properly analyzing it and learning how to identify gems using this data and the process of elimination. After all, gem identification is basically a process of elimination of more than 60 species of gemstones. After making some initial tests, our GIA Graduate Gemologist begins looking at long lists of potential species in an attempt to narrow the list down to just one gem. While it is easy for an expert gemologist to lose his or her way in a sea of data and overlook important clues, SGL follows a list of testing procedures accepted and approved in GIA studies.
Gemstones of similar color undergo non-destructive optical testing until there is only one possible identity. As with all naturally occurring materials, no two gems are identical. The geological environment they are created in influences the overall process so that although the basics can be identified, the presence of chemical “impurities” and substitutions along with structural imperfections create “individuals”.
Various gem identification techniques include identification by refractive index through the use of a refractometer. This is done to determine the gem’s identity by measuring the refraction of light in the gem. Every material has a critical angle, at which point light is reflected back internally. This can be measured and thus used to determine the gem’s identity. Typically this is measured using a refractometer, although it is possible to measure it using a microscope.
With various other identification methods such as “specific gravity” and “spectroscopy” exist, the Graduate Gemologist is able to properly test the gem in question and provide an expert opinion on its identity.