Maw-Sit-Sit Jade from Burma: A Particular Jade Formed by Dynamic Metamorphism and Metasomatism

Mineralogical composition, texture and vibrational spectrum and origin of Maw-sit-sit jade from Burma are studied. The testing methods of optical microscope, EPMA, X-ray powder diffraction analysis, infrared absorption spectrum and Raman spectrum are employed in the research. The results show that mineralogical composition of Maw-sit-sit jade mainly consists of chrome-jadeite[x(Kch) =15%~18%], chromian eckermannite[w(Cr₂O₃) =4% or so], albite, chromiferous-albite[w(Cr₂O₃) 1% or so], kosmochlor[w(Kch) =62%~65%], chromite, etc. The jade is formed by the dynamic metamorphism and metasomatism characterized by mylonitic, metasomatic network and metasomatic pseudomorphous textures. The shape, the location and the semi-height breadth of Raman spectra of the chrome-jadeite and kosmochlor in the range 300~580 cm^-1 are closely associated with the Cr³⁺ concentration, and at the same time are restrained by the bend vibration of Cr-O and Al-O. The research indicates that Maw-sit-sit jade are formed by the superimposition and reformation of multistage dynamic metamorphism and low-temperature hydrothermal metasomatism.