GEMMOLOGY OF MINGXI GARNETS, FUJIAN PROVINCE

Garnets have been found in Mingxi gemstone deposit, Fujian Province, associated with sapphires and zircons. There are two types of garnets. One is purplish red, with main wavelength of 585~588nm and saturation of 0.569~0.629 in their chromatic measurement; the other is brownish red, with main wavelength of 600~595nm and saturation of 0.866~0.939. The purplish red garnet has refractive index of 1.74, density of 3.65~3.78g/cm³ and brownish red garnet, 1.75~1.76 and over 3.8g/cm³ respectively. In the RI-D diagram of Webster(1983), the purplish red garnet belongs to the category of pyrope and most of brownish red garnets fall in the area of almandine pyrope. The conclusion is conformed to the microprobe analyses and X-ray diffraction, which also show that the purplish red is high in Cr while the brownish red high in Fe and Ti. As for the optical absorption spectra of Mingxi garnets, the purplish red has absorption bands at 410 and 570 nm due to Cr ³⁺ in the crystals and the brownish red shows the broad absorption band from 590~400nm with the absorption peaks at 410nm and 510nm.