In Gillian Bradshaw's Imperial Purple, our heroine Demetrias has to weave a purple cloak, a paludamentum, purported to be for the emperor Theodosius, but she soon smells a rat. So does her equally heroic husband Symeon, a purple-fisher, meaning he fishes for murex brandaris, a marine snail and provider of the famous purple dye. They live in the city of Tyre, the most famous place for purple dye making. And so starts a scary adventure.
Wikipedia (handle with care), has an article, Tyrian Purple. Pliny the Elder has a lot on the subject in his BOOK IX. THE NATURAL HISTORY OF FISHES, CHAP. 60-65. (when will Perseus finally fix its pages?)
(37.) Purples also have another name, that of "pelagiæ" there are numerous kinds of them, which differ only in their element and place of abode. There is the mud purple, which is nurtured upon putrid mud; and the sea-weed purple, which feeds on sea-weed; both of which are held in the very lowest esteem. A better kind is the reef-purple, which is collected on the reefs or out at sea; still, however, the colour extracted from this is too light and thin. Then, again, there is the variety known as the pebble-purple, so called from the pebbles of the sea, and wonderfully well adapted for dyeing; and, better than any of them, that known by the name of "dialutensis," because of the various natures of the soil on which it feeds. Purples are taken with a kind of osier kipe of small size, and with large meshes; these are cast into the sea, and in them cockles are put as a bait, that close the shell in an instant, and snap at an object, just as we see mussels do. Though half dead, these animals, as soon as ever they are returned to the sea, come to life again, and open their shells with avidity; upon which the purples seek them, and commence the attack, by protruding their tongues. The cockles, on the other hand, the moment they feel themselves pricked, shut their shells, and hold fast the object that has wounded them: in this way, victims to their greediness, they are drawn up to the surface hanging by the tongue.
(and he has much more to say)
The image of the snail above right is from Wikimedia Commons.
Tyrian Purple of Royalty, A most intriguing problem of hue is nicely written, and The Argonaut Epos and Bronze Age Economic History has lots of interesting references.
For those with JSTOR access, there are two amply illustrated articles:
The Minoan Origin of Tyrian Purple Robert R. Stieglitz, The Biblical Archaeologist Vol. 57, No. 1 (Mar., 1994), pp. 46-54
“BA” Guide to Artifacts: Seashells and Ancient Purple Dyeing I. Irving Ziderman, The Biblical Archaeologist Vol. 53, No. 2 (Jun., 1990), pp. 98-101.
