Gemmological and Mineralogical Characteristic of “Lanshui” Jadeite

In order to investigate the charateristics of the "Lanshui" jadeite from Guatemala, we collected three finished samples and two rough material from the market for non-destructive analysis, including conventional gemmological methods, Fourier transfom infrared spectrometer(FTIR), ultraviolet-visible spectrometer (UV-Vis). Destructive analysis were used for rough materials, such as the thin section observation, XRD and EPMA. The "Lanshui" jadeite is blue to green, glassy luster. Some samples contain several white minerals. The result showed that a spot refractive index of the "Lanshui" jadeite is 1.66 and a hydrostatic specific gravity is 3.33 to 3.35, which are in accordance with the traditional jadeite. The microstructrure showed that the "Lanshui" jadeite is mainly composed of jadeite, with minor zircon and metallic minerals. The jadeite crystals are columnar, fibrous and xenomorphic granular.The EPMA result indicated that the main mineral component is jadeite, with some omphacite. The main component of the "Lanshui" jadeite sample is SiO₂, Al₂O₃ and Na₂O. The w(SiO₂) varies between 56.84%-68.81%, and the w(Al₂O₃) varies between 9.57%-24.16%, and the w(Na₂O) varies between 5.89%-13.71%. The sodic (including jadeite) and sodic-calcic proxenes(including omphacite) were classified by Q-J pyroxenes diagram, where Q=Ca+Mg+Fe²⁺and J=2Na, 0.20< J/(Q+J) < 0.80 is sodic-calcic pyroxenes(including omphacite), J/(Q+J) > 0.80 is sodic pyroxenes. Most J/(Q+J) values of the sample present 0.82-1.00, which belongs to the jadeite, while only a few points vary from 0.50~0.41, which belongs to the omphacite. The XRD result showed that the main mineral of the "Lanshui" jadeite is jadeite. The FTIR spectra of the samples showed the main reflectance band is situated around 1 080 cm^-1 which is consistent with the "jadeite jade" in previous work. UV-Vis absorption spectra of the "Lanshui" jadeite showed the absorption bands around 380 nm and 437 nm were attributed to Fe³⁺ in octahedral coordination, which are in accordance with the traditional jadeite. All the results including conventional gemmological charaterstic, petrological and mineralogical charaterstic, suggest the "Lanshui" jadeite is consistent with the definition of the traditional jadite jadeite.