The body colour of pearls is normally related to the presence of natural colour pigments produced by the mollusc during pearl formation. Another option is to colour pearls artificially, with dyeing being the most readily available method. Often applied to rather low-quality freshwater cultured pearls, these tre

by Dr. M.S. Krzemnicki, first published in Facette 27 (June 2021) It cannot be repeated often enough: any gemstone which contains fissures is prone to be treated with fissure filling substances, either by using a colourless or coloured substances (e.g. oil). Even when the stone comes from a famed mini