Inspection and consideration of the mother shellfish distinction by pearl oyster`s particular optical spectrum

Abstract

According to Dr. Kouji Wada's book "science of a pearl" (1999 Shinju Shinbunsha), it's reported that non-processed Akoya pearls show 3 peaks of absorption at 407nm, 430nm and 460nm on reflection spectrum. It's also stated that these absorption peaks disappear though processing such as heat and alcohol treatment, bleaching and color addition. Therefore, majority of Akoya pearls in the market would not show the above three peaks of absorption on reflection spectrum data.
There are some changes, very small, in Akoya market since the last year. Some Akoya strands are made without any treatments. This attempt is to sell Akoya pearls with natural color condition and also it is expected improvement of durability. Using such non-processed Akoya pearls, we tried to identify them by reflection spectrum. Also we made comparison of both pearls and shells of Akoya and south sea pearls. Then we were able to reach the conclusion that the reflection spectrum analysis is effective to identify Akoya pearls if they are not processed. The reason why Akoya pearls show three peaks of absorption will be also introduced.