The Reason Of The Iridescence In Moonstone And Evaluation Of Color

In this paper,through thin-film observation,infrared absorption spectroscopy,Xray powder crystal diffraction analysis and Electron Microprobe analysis,it is found that different opalescent moonstones belong to Perthite.The white opalescent moonstone is a regular Perthite,and the blue opalescent moonstone is an anti-Perthite,and its Perthite type of the white opalescent moonstone microscopic stripe feldspar can be further divided according to the characteristics of microscopic observation.Blue opalescent moonstone is a cryptocrystalline stripe feldspar.In the exploration of the Iridescence,it was found by BSE and Transmission Electron Microscope that the layered exsolution of Ab-Or caused the light waves inside the moonstone to scattering,and the blue opalescent moonstone was a cryptocrystalline Perthite.The orientation of the exsolution layer is exactly the same,the thickness is much smaller than the wavelength of the visible light,Rayleigh scattering occurs,and the exsolution layer strengthens the short-wavelength blue-violet light to produce blue opalescence;the white opalescent moonstone belongs to the micro-striped feldspar.The exsolution layer is thick and uneven,larger than the wavelength of the light wave,so Mie scattering occurs,and the scattering intensity of the exsolution layer is not different for all wavelengths,so white opalescence occurs.According to the Mie scattering theory,the particle size is larger.The stronger the forward scattering,the greater the thickness of the exsolution layer,and the stronger the moonlight effect of the white opalescence.In the color characterization of the Iridescence,it was found that the achromatic background had a greater influence on the brightness of the blue opalescent moonstone,and less on the white opalescent moonstone with less brightness.As the background brightness decreases(N9.5 to N0.5),the brightness of the opalescence gradually increases,and in the low-light background,the matte color of the moonstone is more distinguishable.By changing the angle of observation,the brightness and chroma of the opalescence will change to some extent,and the hue angle value will not change much.And in the range of observation angles of 25° to 45°,the opalescence has betterbrightness and chroma,and the opalescence has the best color when the observation angle is 35°.