Tyrian purple, the snail dye of emperors

A dye made from sea snails

For most of antiquity the most prestigious colour a person could wear came out of a sea snail. Tyrian purple, named after the Phoenician port of Tyre in what is now Lebanon, was made from the secretions of Mediterranean murex snails, chiefly Hexaplex trunculus, Bolinus brandaris (the Murex brandaris of older books) and Stramonita haemastoma.¹ Each species gave a slightly different shade, from a bluish purple to a reddish one.² Pliny the Elder, writing in the first century AD, said Tyre made the finest purple in Asia,¹ and he rated the dark, blackish tints above the redder ones.³

The colour starts in a gland. Murex snails have a hypobranchial gland that secretes a mucus they use to subdue prey and to protect their egg masses from microbes.³ Straight from the snail the liquid is close to colourless and only turns purple after it has been left exposed to air and light.² The main colouring compound was identified in the early twentieth century by the German chemist Paul Friedländer as 6,6'-dibromoindigo.⁴ It is a close chemical relative of indigo, the blue of denim, with a bromine atom attached to each half of the molecule. Indigo has long been made in factories, but 6,6'-dibromoindigo has never been synthesised on a commercial scale.⁴

Thousands of snails, very little dye

The yields were tiny. Friedländer processed twelve thousand Bolinus brandaris snails and got about 1.4 grams of pure dye.³ The BBC, reporting on modern attempts to recreate the dye, put it at roughly ten thousand snails for a single gram.² Archaeologists find the industry through heaps of crushed shells and purple-stained pottery at dye sites around the eastern Mediterranean, such as Tel Shikmona near Haifa in Israel, which made purple mainly between the tenth and sixth centuries BC. The oldest evidence found so far is earlier still, from a Minoan workshop at Pefka on Crete dated to around 1800 BC.¹

The work was also famously unpleasant. Greek and Roman historians and the Talmud describe dyeing with murex as messy, slow and foul smelling, and Pliny said simply that the smell was offensive.¹

Worth more than gold

All that labour made the finished cloth extraordinarily expensive. Ancient sources and modern historians describe purple textiles as worth their weight in gold, or more.¹⁵ The hardest numbers come from the Edict on Maximum Prices, issued under the emperor Diocletian in AD 301 to cap prices across the empire. Its single most expensive item was a pound of purple-dyed silk, capped at 150,000 denarii.⁶

Rulers used the cost to mark status and then wrote it into law. Julius Caesar tried to keep purple for the elite, and Nero fined people who wore certain shades without permission or sold them to ordinary citizens.¹ By the third century the industry was under tight government control,¹ and in Byzantium the making and selling of purple silk was strictly regulated, with severe punishments for anyone who broke the rules.⁷

Born in the purple

In Constantinople the colour became attached to birth as well as rank. A child born to a reigning emperor was porphyrogennetos, "born in the purple". The phrase pointed to a chamber in the Great Palace where empresses gave birth. The Byzantine princess and historian Anna Komnene described it as a square room, and later scholarship describes its walls, floor and ceiling as veneered with porphyry, a purple stone speckled with white.⁸ Some popular accounts instead describe the room as hung with Tyrian purple.⁹ Either way, the word appears in sources from the sixth century, with its first secure use dated to 846, and it became common in the tenth century, especially around the emperor Constantine VII.⁸ The title mattered in succession because it set a son born after his father took the throne apart from older siblings born before it, and from would-be usurpers.⁸⁹

The trade did not survive the empire. Murex production for the Byzantine court is reported to have ended with the crusaders' sack of Constantinople in 1204,³ and what remained of the craft faded after the city fell to the Ottoman Turks in 1453.³⁷

Perkin's accident

Purple's next chapter began in a London laboratory. In 1856 William Henry Perkin, an eighteen-year-old student at the Royal College of Chemistry, spent his Easter holiday trying to make quinine, the antimalarial drug that then came only from the bark of the cinchona tree.¹⁰ His professor, August Hofmann, had suggested that coal tar waste might be a route to it. Perkin's attempt with aniline left a black residue that stained his glassware and clothes purple and would not wash out.¹¹ He realised it was a dye. On 26 August 1856 he was granted a patent for "a new colouring matter" that dyed silk, cotton and wool lilac or purple, and his father put his savings into a factory at Greenford Green, near Harrow.¹² The dyeworks opened in 1857 on a six-acre site beside the Grand Union Canal.¹⁰¹³

Perkin called his dye aniline purple. The name that stuck, mauve, came from the French word for the mallow flower and was in use in England by 1859.¹⁴ It caught on fast. In 1859 Punch joked that "the Mauve Measles are spreading to so serious an extent" that something had to be done.¹¹¹⁴ According to Imperial College's history of the dye, Queen Victoria wore a silk gown coloured with it at the exhibition of 1862.¹³ Perkin sold the factory in 1874, retired from industry at 36 to do research at home, and was knighted in 1906.¹² Chemists only settled mauveine's exact structure in 1994, when it turned out to be a mixture of two compounds that differ by a single methyl group.¹³

Set side by side, the two purples say a lot about how a colour gets its meaning. Tyrian purple signalled power for so long partly because it took thousands of snails, a stretch of coast and a protected craft to make any at all. Mauve started as a stain from coal tar waste and within a year was being made in a dyeworks by a canal in Middlesex, for anyone who could afford a dress.

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1. Sara Toth Stub, The price of purple, Archaeology, 2020.
2. Zaria Gorvett, Tyrian purple: The lost ancient pigment that was more valuable than gold, BBC Future, 2023.
3. Wikipedia, Tyrian purple.
4. Wikipedia, 6,6'-Dibromoindigo.
5. Mary Randolph, In the ancient world, this pigment was worth more than gold, Smithsonian Magazine, 2026.
6. Wikipedia, Edict on Maximum Prices.
7. Philippa Scott, Millennia of murex, AramcoWorld.
8. Wikipedia, Born in the purple.
9. Nick Kampouris, The true meaning of Byzantium's "purple-born" emperors, Greek Reporter, 2026.
10. Science History Institute, The story of mauve, Science History Institute.
11. Smithsonian Magazine, How malaria gave us mauve, Smithsonian Magazine.
12. Science Museum Group, William Henry Perkin, Science Museum Group Collection.
13. Imperial College London, Perkin and mauveine, Imperial College Department of Chemistry.
14. Wikipedia, Mauveine.