Characteristic of Hetian Yu from Luodian, Guizhou Province, China and Its "Piebald" Inclusions

Since the discovery of Hetian Yu deposits in Luodian, Guizhou Province, China, a large number of gemmological studies have been carried out and gradually formed a system. However, there are few studies on the commonly distributed "piebald" inclusions that have significant origin characteristics on or near the surface of the Hetian Yu. To obtain the spectral characteristics, inclusion features and chemical compositions of Hetian Yu from Luodian, conventional gemmological tests, microscopic photography, infrared spectroscopy, Raman spectroscopy and electron probe had been implemented. The results showed that the colour of Hetian Yu samples from Luodian is mainly gray white, bluish white and cyan. Besides, there are possible white bands and black to brown "piebald" inclusions on Hetian Yu. After polishing, the samples show a weak grease luster, a clear porcelain sense and slightly transparent. The specific gravity ranges from 2.81 to 2.90. The average chemical formula of Hetian Yu from Luodian is (Ca²⁺ _1.75Na⁺ _0.05K⁺ _0.02)_1.82(Mg²⁺ _4.96Al³⁺ _0.03Fe³⁺ _0.02)_5.01Si⁴⁺ _8.07O₂₂(OH)₂. Both infrared spectra and Raman spectra show characteristic spectra of tremolite. Some samples show absorbing at 855 cm^-1 in the infrared spectrum due to the accessory mineral of diopside.EDS mapping images and Raman spectrum, indicate that the "piebald" inclusions are enriched with Mn elements, and their broadband scattering around 640 cm^-1 indicates that they are manganese oxides, which is related to the Mn-O symmetric stretching vibration of the MnO₆ octahedron. Meanwhile there can be accompanied by scattering peaks at 154, 280, 710 cm^-1 and 1 085 cm^-1 caused by calcite accessory mineral.