Tyrian purple, also known as royal purple, imperial purple or imperial dye, is a natural purple-red dye which is extracted from certain sea snails, and which was first produced by the ancient Phoenicians. This dye was greatly prized in antiquity because it did not fade, instead it became brighter and more intense with weathering and sunlight. Tyrian purple was expensive: the 4th-century-BC historian Theopompus reported, "Purple for dyes fetched its weight in silver at Colophon" in Asia Minor.

The dye substance is a milky mucous secretion from the hypobranchial gland of one of three species of medium-sized predatory sea snails that occur in the eastern Mediterranean Sea: Bolinus brandaris, the spiny dye-murex; the banded dye-murex Hexaplex trunculus; and the rock-snail Stramonita haemastoma. (Read more...)