Influence Of Nacre Thickness And Crystal Structure Characteristics On Interference Color And Luster Of Cultured Akoya Pearl

Interference color and luster are representative characteristics that determine the beauty and economic value of cultured Akoya pearls. To understand the mechanism of appearance, we investigated the influence of thickness of the whole nacreous layer (range: 0.28-1.57 mm) and crystal microstructure, i.e. the thickness of one CaCO3 crystal tablet (0.32-0.42 mu m) and the coefficient of variation of crystal thickness on the intensities of interference color and luster of pearls. A significant positive correlation between interference color and both whole thickness of nacre (r=0.669-0.863) and crystal tablets (r=0.613) was detected. A negative correlation between interference color and coefficient of variation of crystal thickness (r=-0.651) was also observed. On the other hand, no significant correlation was observed between luster and these crystal structure factors. Results of multiple regression analysis suggest that the degree of influence on the interference color is large in order of thickness of nacre, thickness of one crystal tablet, and coefficient of variation of crystal thickness. Our results will contribute to the development of a technique for producing high-quality Akoya pearls by enhancing their interference color.