Clinochlorite: A New Type of Tian Huang lmitation

Tian Huang, which has its own features in shape, skin and grain, is a kind of jade produced at Shoushan Village in Fujian Province. Its main mineral component is dickite or nacrite. However, there are lots of imitations in the market due to the high price of Tian Huang. In this paper, a new type of Tian Huang mitation which is mainly composed of cli-nochlorite is identified, The Tian Huang imitation is yellow to brownish yellow in colour,and translucent with glassy luster. What’s more, “radish grain” and “red grille” can be found in the Tian Huang imitation. As a result, it is difficult to distinguish the imitation from Tian Huang by only judging the exterior appearance. However, the Tian Huang imitation is more transparent than Tian Huang. The measured refractive index is 1.585 and the specific gravity is 2.81 for the Tian Huang imitation, which are higher than that of Tian Huang. By X-ray powder diffraction analysis, clinochlorite is characterized by the diffraction peaks at 14.39,7.14,4. 74,3.55 Å while Tian Huang is lack of 14 Å. Both of the Tian Huang imitation and Tian Huang show their hydroxyl absorptions between 3 700-3 400cm^-1 in the infrared spectra, It is worth emphasizing the difference that the Tian Huang imitation has faint shoulder-shaped absorptions at 3 679,3 671,3 651 and 3 629 cm^-1 over a broad absorption, while Tian Huang has sharp absorptions at 3 700,3 645,3 625 cm^-1,Hence, it is not difficult to identify Tian Huang from clinochlorite by means of X-ray powder diffraction, infrared spectrum, refractive index and specific gravity measurement.