gems, jade, pyroxene jade, jadeite, fei cui, synthetic jadeite, synthetic fei cui, simulants, HPHT

Jadeite, commonly known as jade, is a rare gemstone composed primarily of sodium aluminosilicate with the chemical formula NaAlSi₂O₆. Its physical and chemical properties are closely tied to geological processes, making it a key subject in both gemological and geological research. This dissertation investigates the high-temperature and high-pressure (HTHP) synthesis of sodium aluminosilicate jadeite, including systems doped with various oxides, in an effort to simulate natural jadeite formation environments. By studying the experimental conditions and the mineralogical and physical characteristics of synthetic jadeite, the work aims to explore the mechanisms of natural jadeite formation and its coloration process. The color and texture of jadeite are closely related to its crystallinity and internal structure. Key to producing gem-quality synthetic jadeite is enhancing the conversion of amorphous glass material to jadeite, maximizing transparency, and enabling coloring ions to enter the jadeite crystal lattice for stable coloration. This study optimized the synthesis assembly and processing of sodium aluminosilicate jadeite, successfully producing samples doped with different oxides and yielding several innovations: (1) An optimized experimental chamber for HTHP synthesis was designed, using a sodium chloride–zirconia composite as the pressure-transmitting medium. This ensured pressure and temperature stability while preventing sample breakage due to sticking with the medium. (2) The preparation process for doped glass was improved by mixing metaaluminate and sodium silicate nonahydrate with trace oxide colorants. Multiple quenching steps produced high-quality doped glass, effectively eliminating the common “black spots” and “color patches” seen in synthetic jadeite. (3) Jadeite synthesis was carried out under various pressures, establishing the pressure-temperature ranges required for HTHP synthesis. As pressure increased, the necessary synthesis temperature also rose. Undoped samples exhibited uniform, dense textures and no cracking, with a homogeneous white appearance, a pure jadeite composition, and typical silicate chain morphology and vibrational characteristics. (4) By doping with 0.4 wt.% of TiO₂, V₂O₅, Cr₂O₃, MnO, Fe₂O₃, CoO, NiO, and CuO, jadeite samples with gray, apple green, emerald green, pink-purple, light yellow-green, cobalt blue, yellow, and sky blue colors were successfully synthesized. XRD analysis confirmed that all samples were composed primarily of jadeite. When doped with 1.0 wt.% MnO, the jadeite turned bluish-purple, with synthesis possible at pressures as low as 2.5 GPa. (5) Microstructure, Raman, and infrared spectroscopy of the high-quality doped jadeite samples showed that those synthesized at higher pressures exhibited a fibrous woven texture resembling natural jadeite. At 5.0 GPa and 1450 °C, samples doped with 0.4 wt.% TiO₂, MnO, Cr₂O₃, and Fe₂O₃ exhibited strong Si–O tetrahedral vibrational peaks at 373 cm⁻¹ and 698 cm⁻¹, identical to those of natural jadeite, with no extraneous peaks. Infrared spectra confirmed typical jadeite absorption features. (6) Elemental and UV–Vis spectral analysis of the doped jadeite samples indicated elemental compositions consistent with natural jadeite. The concentrations of color-causing ions matched the doping levels, suggesting effective incorporation into the crystal lattice. UV–Vis absorption spectra showed distinct ion absorption peaks corresponding to each dopant, consistent with the mechanism of coloration through ion-based color centers.