Structural colors of pearls.

The luster is the most important characteristic of pearls, whose colors depend on periodic structures of aragonite crystal layers and conchiolin sheets. We here propose an optical model for analyzing the structural colors of pearls that includes the transmission, reflection, and scattering of light in pearls. Unlike other structural color materials, internal light scattering and its transmission are the keys to understanding the optical properties of pearls. The appearance of pearls is determined by the superposition of transmitted and reflected light. The transmission and reflection spectra of pearls calculated using the proposed model show good agreement with experimental results. We also demonstrate the rendering of images of pearls using the calculated spectra. Furthermore, the appearance of pearls with different layer thicknesses are predicted by calculation based on the optical model.