Gemmological Characteristic of Quartzose Jade by Metamorphism

The metamorphic quartzose jade in gemmology is reported for the first time. In this paper, the gemmological characteristics of the samples were summarized by means of polarizing microscope and reflecting microscope, electron probe, X-ray powder diffraction and infrared spectroscopy.The test results showed that the sample is composed of recrystallized quartz and a small amount of low-sodium feldspar. The quartz was a microcrystalline grain with a maximum particle size of 0.01 mm. Electron probe magnification 2 000× second electron image (SE) shows that the sample has a dense structure formed by 1—2 μm micron fine scales superposed with each other. The degree of crystallization of the sample decreases gradually from the shell to the transition layer to the interior and most of the internal quartz was cryptocrystalline and the grain boundaries could not be seen. The mass fraction of SiO₂ in the quartz electron probe data is lower than the theoretical value. The total chemical composition of ilmenite is less than 100% due to the production of H₂O during alteration.The infrared spectra showed obvious splitting near 900—1 200 cm^-1 and 5 200 cm^-1, which fully proved that the material was a kind of quartz jade formed by metamorphism that contains water.