Gemmological Characteristic and Identification of Gem-Quality Benitoite

Benitoite is a rare gemstone originated in San Benito County, California, USA, which has gotten more and more attention. In order to identify the benitoite correctly and rapidly, the authors investigated samples with the help of conventional gemmological identification methods and advanced instrumentations including energy dispersive X-ray fluorescence spectrometer, UV-Vis spectrophotometer, Fourier transform infrared spectrometer, and Raman spectrometer. The results showed the polished facet of benitoite is sub adamantine luster, and the refractive index exceed maximum of refractometer. Under short-wave ultraviolet light the benitoite showed strong bule-white fluorescence. It is usually observed that in benitoite there are many hair-like, needle-like, short-cylinder-like solid inclusions. Vanadium perhaps causes the benitoite's blue colour. Fourier transform infrared spectrum results showed strong absorption peaks at 453,502,773,942,1 063 cm^-1 and Raman spectrum results showed strong absorption peaks at 220,575,935 cm^-1, which are the identification bases of benitoite.