Light Interference Phenomena Observed in Pearls with Pale and Dark Colour and the Measurement

Abstract

The essential beauty of pearls comes from "teri", a Japanese term to express a combined effect of luster and interference colour seen in pearls. "Teri" is not a simple equivalent to luster. "Teri" appears due to light interference from the textures of pearls. "Teri" exhibited by pale colour pearls, like Akoya pearl, appears phenomenologically opposite to that exhibited by dark colour pearls, like kurocho. How "teri" appears is theoretically analyzed for the two series, pale and dark colour pearls. Based on these analyses, optical methods combined with computer evaluation are newly designed to quantitatively evaluate "teri" of pearls in the two series.