Abstract: Gemmological characteristics and mineral components of black cyan nephrite from Dahua, Guangxi were tested and analyzed by conventional gemmological methods, X-ray powder diffraction and electronic microprobe.The results showed that the relative density of black cyan nephrite samples from Dahua, Guangxi ranges from 3.02 to 3.13, with an average of 3.08.The refractive indexes of five testing samples range from 1.62 to 1.63, which are in the larger value of the nephrite standard parameters.The X-ray powder diffraction analyses showed that the major mineral component of the five testing samples is actinolite and the minor minerals are sanidine, pyrite and dolomite.The electron microprobe showed that constituent of the five testing samples is actinolite, in accord with X-ray powder diffraction results.