Ultraviolet Testing And Gemstone Identification


Step 3: Practical Gemology

Lesson 17

Extremely rare benitoite has a strong blue fluorescence under UV light. “Benitoite and neptunite under UV Light” by Géry Parent. Public Domain.
Extremely rare benitoite has a strong blue fluorescence under UV light. “Benitoite and Neptunite under UV Light” by Géry Parent. Public Domain.

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 light, is one of the easiest tests you can perform. It may be the only other test you need. 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 this in an early stage of your examination can …

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