Gemmological Characteristic of Nephrite with Dendrite Pattern from Dahua, Guangxi Province

The nephrite with dendrite pattern from Dahua, Guangxi Province, is a special kind of nephrite jade. The nephrite with variety of dendrite pattern ("Shuicaohua") is an unique species of nephrite from Dahua, Guangxi Province. In this paper, the nephrite with variety of dendrite pattern was studied with gemmological tests, polarizing microscope, electron microprobe (EPMA), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray diffraction(XRD). The gemmological testing results showed that the refractive index of samples is between 1.59 and 1.61 by point measurement and its average is 1.60. The density is between 2.89 and 2.94 and its average is 2.91. The surface of samples have variety of dendrite pattern("Shuicaohua").
By observing the mineral slices under polarizing microscope, the mineral component of the samples is tremolite. The textures of tremolite are classified in two types. One is fibrous intergrowth crystalloblastic texture, and the tremolite grains are distributed uniformaly and its content is more than 95% in general. The other is flaky intergrowth crystalloblastic texture, and the tremolite grains is distinctly larger and its content is less than 5%.
According to the electron microprobe (EPMA) test, the content of MnO in white-gray tremolite (without dendrite pattern) is between 0.21% and 0.35%, and the content of MnO of dendrite pattern is between 0.94% and 3.96%. It is concluded that the dendrite pattern ("Shuicaohua") is caused by MnO. The formation of dendrite pattern ("Shuicaohua") should be probably due to fracture filled with MnO.