Correlation Between Color and Bubble Microstructural Characteristics in Baltic Amber

Baltic amber exhibits a wide range of colors and has attracted considerable attention in materials science. Previous studies have mainly focused on the origin and formation characteristics of beeswax-amber, while the relationship between beeswax-amber color and the microstructural characteristics of internal bubbles remains poorly understood. Ten beeswax-amber specimens exhibiting a color gradient from yellow to white were selected. Scanning electron microscopy (SEM) was used to examine and analyze their internal structures, with a focus on documenting bubble size, number, and density characteristics. Ultraviolet (UV) illumination was employed for qualitative optical observation, and Fourier-transform infrared (FTIR) spectroscopy was conducted to identify component phase and spectra. The correlation between bubbles and color was analyzed to infer the origin of white beeswax-amber's coloration and explore the mechanisms underlying beeswax-amber's color variation. Results indicate that beeswax-amber coloration is closely linked to its microscopic bubble characteristics. The microstructure satisfies conditions for Mie scattering, some white beeswax-amber samples contain abundant nanoscale bubbles, triggering a combined effect of Rayleigh and Mie scattering. These results demonstrate that the color of Baltic amber is governed not only by its intrinsic body color but also by the synergistic optical effects arising from internal bubble microstructures, providing a physically grounded explanation for its diverse appearances.