Acta Petrologica et Mineralogica

The serpentine jade in Kuancheng County, Hebei Province has a delicate structure and can appear in flesh red or green colors. It is called "Rehe Jade" in the local market. This article systematically analyzed it through conventional gemological testing combined with laser Raman spectroscopy, electron probe, X-ray powder diffraction, laser ablation plasma mass spectrometry, and visible light absorption spectroscopy. Its radiation safety was tested by gamma spectrometer. The results show that the refractive index and relative density of the flesh red samples are both low, with 1.54~1.55 and 2.33~2.43. The flesh red samples contain main mineral of clinochrysotile and auxiliary minerals of calcite and diopside with fiber interwoven texture, and column-grain interwoven texture, and residual biological skeleton texture can be seen locally. The content of Fe and Mn in flesh red samples are relatively high, ranging from 184.9×10^-6~951.7×10^-6 and 106.4×10^-6~287.3×10^-6,respectively. The green sample has the refractive index of 1.55~1.56 and the relative density of 2.58~2.62. The green samples contain main mineral of antigorite and auxiliary minerals of talc and mackinawite, with more delicate fiber interwoven texture. The content of Fe in green samples is extremely high, ranging from 5 979×10^-6~6 359×10^-6. Combined with visible light absorption spectrum test, it is considered that the comprehensive effect of Fe³⁺, Fe²⁺, and Mn³⁺ is the main reason for the appearance of flesh red in samples, while the effect of Fe²⁺ and Fe³⁺ is the main reason for the green color. The radioactivity test result shows that the internal and external radiation indexes, and specific activity values of Kuancheng serpentine jade are lower than the standard requirements, and the sample has no radioactive hazard to the human body.

serpentine jade; gemology; mineralogy; color genesis; radioactivity