Gemmological Characteristic of Sugilite Imitation

Recently, sugilite has become popular among jewelry lovers, with the hot market, its imitations have appeared. However, few researches have been done on sugilite imitations. The conventional gemmological and spectroscopic characteristics of a kind of sugilite imitation product that appeared recently was studied by conventional gemmological tests, Fourier transform infrared spectrometer(FTIR), Raman spectrometer, and UV-Vis spectrometer. The results showed that the sugilite imitation has uneven surface colour, with colour enrichment at pits and fissures, and colour loss after alcohol wiping. Infrared spectroscopic analysis showed that this sugilite imitation mainly contains two minerals, serpentine and calcite, with infrared characteristic absorption peaks of 1 420, 874 cm^-1 and 712 cm^-1 for calcite and 3 686, 1 083, 968, 611, 570 cm^-1 and 436 cm^-1for serpentine.Raman spectral analysis showed Raman shifts of calcite 150, 277, 708, 1 080 cm^-1, dolomite 168, 291, 717, 1 090 cm^-1, and serpentine 127, 220, 373, 457, 515, 628, 682, 1 039 cm^-1. The strong broad absorption band around 580 nm is visible in the ultraviolet visible spectral analysis, which is presumed to be stained by an external stain containing Mn³⁺. This imitation of sugilite is clearly different from sugilite, which is dyed by Lantian jade. It should be designated as Lantian jade (dyed) according to the national standard of Gems-Nomenclatur.