Ultraviolet Testing and Gemstone Identification

Step 3: Practical Gemology

Lesson 17

Gemstone identification starts with measuring a specimen’s refractive index (RI) and specific gravity (SG). These two tests will leave you with a short list of possible materials. However, more testing is necessary for a positive identification. Ultraviolet testing, checking a gem’’s reaction to ultraviolet (UV) light, is one of the easiest tests you can perform. It may be the only other test you need.
Reading time: 7 min 59 sec
ultraviolet testing - benitoite
Extremely rare benitoite has a strong blue fluorescence under UV light. “Benitoite and Neptunite under UV Light,” photo by Géry Parent. Public Domain.

Additionally, ultraviolet testing can expose some gemstone treatments and assembled stones. The enhanced layers of diffusion-treated gems, oils used as fillers in emeralds and other gems, and the components of assembled stones often have different fluorescent qualities than the rest of the specimen material. Seeing …

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