Abstract

Freshwater cultured pearls show generally white, orange pink and purple series. This study suggests the identification point of freshwater black cultured pearl based on comparative analysis of a rare freshwater cultured pearl of natural black color which is produced less than 0.1% from freshwater cultured pearl production. Various identification methods has somehow been established for other black cultured pearls (treated Akoya black cultured pearl, natural Tahiti black cultured pearl, treated Tahiti black cultured pearl and treated Freshwater black cultured pearl). Naturally colored Freshwater black cultured pearl has two characteristic absorption patterns in UV-Vis spectra, which are 380 nm-400 nm and 480 nm-500 nm. Unlike naturally colored Tahiti black cultured pearl, the absorption spectrum at 700 nm cannot be found from freshwater black cultured pearl. It can be concluded that the color was not processed due to its very high reflective Index (70%). Judging from the contents of Mn and Sr elements found from ED-XRF analysis, it is possible to identify this as freshwater cultured pearl. Since the content of Ag is ranged under 0.1%, it seems to be that the possibility of silver nitrate treatment is very low. Moreover, by conducting silver nitrate treatment on series of white Akoya cultured pearl, freshwater cultured pearl and Tahiti black cultured pearl of light black or gray color, the result of this study provides a way to identify whether black color pearls of any origin found in marketplace are treated or not.