What was the ‘purple cloth’ that Lydia of Thyatira dealt in?

"One of those listening was a woman from the city of Thyatira named Lydia, a dealer in purple cloth." - Acts 16:14

From as early as 1500 BCE, Phoenicians had started using the reddish-purple dye made from the secretions of several species of sea snails. Extracting the dye involved large quantities of snails and was labour-intensive. The dye did not easily fade but actually brightened with weathering and sunlight. Hence, the dye, and the dyed cloth, was highly valued.

During the 1st century CE, Thyatira, in present-day Turkey, was a famous centre for dyeing and trading in purple cloth. It had a Christian church, one of the recipients of the Seven Letters to the Churches in Revelation 2-3.

Paul met Lydia in Philippi in Greece, very soon after he had crossed over to Europe. She was probably an agent for a firm in Thyatira which traded in the purple dye or and dyed fabric. She is considered the first documented Christian convert in Europe. After her conversion, she offered hospitality to Paul and his companions while they remained in Philippi.