Dyed black pearls are a growing trend. Many low-quality cultured pearls are dyed. Dyed pearls can often be detected just by looking at them because of their artificial pigment. However, sometimes it may be difficult to identify if a pearl has been dyed. If it is important to determine whether a pearl has been dyed, the following steps can be taken:
Black cultured pearls can be tested for dye by adding a small solution of water mixed with a small drop of nitric acid (1/4 cup water and one small drop nitric acid) to the surface of the pearl. If the color starts to come off, then it is dyed. HOWEVER, this solution can be very harmful to the pearl surface so immediately add baking soda to the mixture to keep the pearl from being damages. Some dyes need to be tested using more advanced technology.