Gemmological Characteristic and Identification Method of Dyed Tremolite Imitating Natural Black Tremolite Jade (Mo Yu)

In this study, Raman spectroscopy, UV-Vis spectroscopy, Infrared spectroscopy, X-ray fluorescence spectroscopy, laser ablation inductively coupled plasma mass spectrometry and other modern testing methods were used to compare the "Mo Yu" called by the sellers on the market with tremolite from Luodian, Guizhou and Dahua, Guangxi, and Mo Yu from Xinjiang. The results show that this kind of "Mo Yu" called by the sellers is dyed to imitate natural black tremolite. Compared with natural tremolite jade, it is found that this kind of dyed tremolite is mostly subtranslucent or opaque, and colour zonation can be found on the cross section of some samples. Under the long-wave ultraviolet light, special fluorescence phenomena can be observed, and some samples show the pattern of water plants. Raman spectra confirm that the main component of the sample is tremolite, 1 580 cm^-1 vibration of lumpy, disseminated, and irregular banded graphite can be seen at the treated site. Ultraviolet-visible absorption spectra show that natural tremolite jade samples have absorption peaks near 270 nm and 950 nm, which is unobservable with dyed tremolite jade samples. The infrared spectrum show that the content of constitution water in dyed part decreased, its integral area of the infrared spectrum is reduced about 2.6%. XRF and LA-ICP-MS tests show that the dyed tremolite jade samples have similar chemical compositions with tremolite jade from Dahua, Guangxi, both of which have high Mn content and similar distribution patterns of rare earth elements. According to the colour observation, composition, Raman spectra, and other characteristics of the dyed tremolite jade samples, combined with the authors' experimental results on tremolite from Dahua and Luodian, it is basically determined that the dyed tremolite jade samples in this study are the products of Dahua tremolite treated with sugar and acid.