The Tyrian purple dye block from Roman Britain was produced from large quantities of sea snails, which may have been used for frescoes. Archaeologists and volunteers discovered an extremely rare object during an excavation of a Roman bath in the city of Carlisle, northern England, which was occupied by Rome from 43-410. Newsweek reported on May 3. Analysis showed that the object, made of a soft purple substance, contained beeswax and the element bromine, indicating that it is a solid sample of Tyrian purple dye, a highly valuable artificial pigment in ancient times.
Purple dye is secreted by some carnivorous sea snails living in the Mediterranean region. Producing Tyrian purple is extremely difficult, requiring thousands of sea snails to create just 1 gram of dye. This made the substance extremely expensive in Roman times, reserved for use by the upper class. Frank Giecco, an archaeologist with mining consultancy Wardell Armstrong, described Tyrian purple as the most expensive and sought-after color in the world throughout history.
Tyrian purple was first produced in the 2nd millennium BC by the Phoenicians, originating from the coastal region of the Levant. The dye was produced in Tire, Lebanon, and other Mediterranean areas. The dye sample found at Carlisle was likely used to paint frescoes, according to Sarah Irving from Cumberland Council, which collaborated on the excavation project.
The discovery of the Tyrian purple dye block at Carlisle is considered unique, as it represents possibly the only solid sample of unused paint pigment in the Roman empire. This finding sheds light on the intricate and costly process of creating this highly sought-after dye in ancient times.