Dick Petit encouraged me to contact André Verhecken, a chemist who is interested in Tyrian purple. He responded quickly and here is his contribution to the discussion on Conch-L. Andrew K. Rindsberg Geological Survey of Alabama ++++++++++++++ Dear Dr Rindsberg, It's nice to hear from other people interested in Tyrian purple ! Most of the questions you suggest have been treated in my paper "The indole pigments of Mollusca", Annales de la Société royale zoologique de Belgique, 119 (2): 181-197 (1989). [SNIP] There is also my "Experiences with mollusc purple", La Conchiglia, 22 (250-252):32-34, 46. with color illustrations of the formation of the purple dye. So, in this context you will understand that I don't feel like repeating myself. As to you last question (imitations of purple): this has certainly been done, already in Antiquity, with other natural dyes. And early this century, a synthetic dye was made before the structure of the mollusc purple was known; and afterwards they turned out to be the same! But the synthetic dye never was a commercial success, because the color shade was not good enough commercially. As a matter of fact, there is a huge literature on Tyrian or mollusc purple. The Austrian scholar published a 4-volume work on the subject: "Ein Beitrag zur Purpurkunde", Mayer & Müller, Berlin (1898, 1906, 1908 and 1911). It seems to be a rare work, perhaps it is only in a central library in the US. If you have other questions regarding purple, please don't hesitate to contact me. Sincerely, André Verhecken