Purple

Purple owes its symbolism above all to the extreme cost of the ancient dye. Tyrian purple was extracted from the glands of murex sea snails on the Phoenician coast, and it took many thousands of the creatures to dye a single garment, making purple cloth literally worth more than its weight in gold and restricting it, under Roman and Byzantine sumptuary law, to the emperor and the highest ranks, to be born to the purple, porphyrogenitus, was to be born to one born a reigning emperor. From this material fact flows the whole later symbolism of purple as the colour of royalty, sovereignty and the highest authority, sacred and secular alike; a bishop's purple and a cardinal's red descend from these dye hierarchies.

Purple is also, in the Christian liturgy, the colour of Advent and Lent, penitence and preparation, and of mourning. Its association with the spiritual and the mystical, and in the modern chakra scheme with the crown centre, extends this long identification of purple with what is highest, whether in rank or in aspiration.

Purple in the ancient Mediterranean means one specific dye, and the reason it signified power is that making it was appalling.

The dye comes from marine snails, principally Hexaplex trunculus and Bolinus brandaris, and from a single small gland in each animal. The secretion is not purple when taken; it is a pale fluid that develops colour on exposure to light and air. Producing a usable quantity required enormous numbers of snails, and the processing involved crushing and prolonged salting and simmering. The stench of the dyeworks is remarked on by ancient authors, and the mounds of crushed shells at Tyre and Sidon are still identifiable archaeologically.

Pliny describes the process and its cost. Roman sumptuary law restricted the deepest purple to the emperor, and Byzantine practice went further, with the phrase born in the purple referring to a chamber of the imperial palace. What the law was regulating was less a colour than a demonstration of expenditure.

The industry did not survive the fall of Constantinople in 1453, and the technique was genuinely lost for centuries. Modern reconstructions have established the chemistry, and the principal colourant is dibromoindigo, chemically a close relative of indigo.

The point that matters for reading the sources is that Tyrian purple was not a fixed hue. Ancient descriptions place it anywhere from a deep red to a blackish violet depending on species, concentration and process, and the modern mental image of a clear bright purple is probably wrong for most of what the texts describe.