Identification of dyed turquoise

染色绿松石

The dyed turquoise encountered in daily testing is often accompanied by filling treatment. The dye is often mixed in artificial resin and filled into turquoise. The purely dyed turquoise is very rare. Therefore, when testing, we often detect the filling in the infrared spectrum before further UV-visible absorption spectroscopy to determine whether the sample is dyed.

NGTC Beijing Laboratory recently detected a turquoise rosary. After infrared spectrum detection, no absorption peak of artificial resin was observed. Some particles only saw a small amount of wax absorption peak. It was judged that the sample was not filled and magnified, and several turquoise surfaces were found. It was found that the color was different in depth, and it was cluster-like and spot-like. The blue powdery substance was enriched in the sample depression, which was suspected to be dyed. Subsequently, UV-visible absorption spectroscopy was performed to verify that the dye absorption peak at 677 nm was observed, which proved that these turquoise beads were indeed dyed.

Compared with the dyed and filled turquoise, the dyed turquoise is more uneven in color distribution. It can be effectively screened by magnification inspection and further confirmed by UV-visible absorption spectroscopy. We have consulted Teacher Dai Hui from Anhui Quality Inspection Station. She pointed out that the dyed turquoise samples that have been made at present have absorption peaks of 677 nm, but there is no such peak. It can not prove that there is no dyeing treatment, and other dyes may exist.

Therefore, when we are testing turquoise, it is important to analyze the various data detected by large instruments, but conventional inspection items cannot be ignored. If a magnifying inspection characteristic similar to the above sample is found in the detected turquoise sample, even if the ultraviolet-visible absorption spectrum does not show an absorption peak of 677 nm, it should be confirmed that the sample is subjected to dyeing treatment.

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