Special Optical Effect of Amber from Myanmar

Amber from Myanmar is the oldest amber of all origins, which has experienced the longest geological process and the most complex formation process. There are many kinds of special optical effects of amber from Myanmar, such as "oil gloss" phenomenon and "retaining light" phenomenon. Those special optical effects have not yet been studied scientifically and systematically so far. In this paper, fluorescence spectrophotometer and transient phosphorescence time-resolved spectroscopy were used to measure amber from Myanmar with special optical effects. The following conclusions are obtained: (1) The fluorescence spectra of amber from Myanmar have good uniformity, and have 432 nm and 470 nm fluorescence centers, which caused bluish violet fluorescence when exposed to ultraviolet; (2) Both black-tea amber and green-tea amber with the phenomenon of "oil gloss" have 625-650 nm bimodal luminescence centers, and the pink fluorescence on its surface is caused by the red fluorescence of the luminescence centers. At the same time, the pinkish red fluorescence of black-tea amber under long-ultraviolet light is also formed by the superposition of blue fluorescence and red fluorescence of black-tea amber powders; (3) The "chameleon" amber with "green film" effect on its surface has strong blue and purple luminescence centers at 437 nm and 470 nm, and the surface of "chameleon" shows dark green. This "green film" is the superposition of the luminous center and the deeper brown body colour; (4) The essence of the "retaining light" phenomenon in amber from Myanmar is phosphorescence, in which the lifetime of phosphorescence at 432 nm is between 0.32 s and 0.48 s; the lifetime of phosphorescence at 470 nm is between 0.31 s and 0.42 s; the lifetime of phosphorescence at 650 nm is between 0.21 s and 0.25 s; (5) The luminescence behavior of amber with different luminescence centers is different, which may be caused by different wavelength excitation, or the contribution rate of two or more fluorescent substances to the luminescent behavior of amber varying with the wavelength excitation.