The historical importance of Japanese akoya, South Seas, and Tahitian pearls is key to the cultured pearl industry. Early courses taught by the GIA and subsequent grading systems developed by Gemworld incorporated key elements of grading including color, shape, luster, nacre, and matching. As the Chinese freshwater product came to market in great quantities, the new competition resulted in Japanese akoya being harvested sooner, hence they now had thinner nacre. The changes in product began to appear around the mid-1990s. Gemworld Grading System In 1992 Gemworld developed our first grading system for cultured pearls. At that time, it did follow closely the GIA grading factors. Then, in 1998 GIA revised the pearl course and introduced new criteria, especially with nacre thickness terms for reasons stated above. In recent years, Gemworld also revised our grading system to reflect the new criteria as taught by GIA along with our own opinion of value factors. Although we developed grading for many varieties, the grading that appears here is only for the Japanese cultured and the Chinese cultured products. The summary of the grading system that we offer is to help jewelers and appraisers understand the relationship between the grading factors. It also addresses the newer terminology of nacre which is more lenient than in the past. The system assigns a grade from ....