<< I read a Scientific American article years back and contemporary scientists had found the source of
this blue historically. It is a sea snail in the Mediterranean and though there are many types
this one was found in a certain area as I remember. The lovely aspect of it is the mucus it
secretes turns a sort of purplish blue,>>
I believe that is "from the mollusks Purpura, Thais and Murex, and associated with the dress and rank or office of emperors, consuls, kings etc." (From my cheap desk encyclopedia)
The charming Tony Robinson covered the extraction process in his "Worst Jobs in History" television series.
The unpleasant nature of the procedure and the spareness of the result made it only available to those of high rank.
As a humble salt printer I thought that gum printing looked like another worst job in history!
Regards - Ross