The Rapaport Price List is the primary source of diamond prices and market information. It is the international benchmark used by dealers to establish diamond prices in all the major markets. 

subscription to the Rapaport Diamond Price List offers you access to the Rapaport Price List with diamond prices based on the size, color and clarity of each diamond.

The Price List is updated weekly Thursdays at 11:59 p.m. EST and reflects changes in the global diamond markets. http://www.diamonds.net/prices or http://www.rapaport.com