They would brutally crush over 10,000 individual snails of the genus Murex to extract one gram of the dye, making it almost priceless. The ancients obtained a photo-reactive dye for cloth from sea snail excretions, which changed color from yellow to purple when exposed to sunlight and air. Mysterious, hypnotic, and coveted for its rareness, the color has represented royalty for thousands of years. What human activity could push a beautiful shellfish to the brink of extinction? It's not pollution as you might think, but the color purple. The University of Houston presents this series about the machines that make our civilization run, and the people whose ingenuity created them. It was first used in the title of a paper in Economic Geology in 1947 but did not gain widespread use until the 1970s, following the publication of seminal papers on porphyry models and genesis by Lowell and Guilbert ( 1970) and Sillitoe (1972, 1973).Today, we see purple. It was slow to catch on in the geological literature. Emmons in his 1918 textbook The Principles of Economic Geology, but it was originally used more as an engineering and economic description, as in Parsons’ 1933 book The Porphyry Coppers. As a result of the close spatial and genetic relationship to porphyry stocks, they became known as porphyry copper deposits. Mining of the first porphyry copper deposits, which were originally called disseminated or low-grade copper deposits, started in 1905.

The name evolved in the field of igneous petrology to include all rocks with a porphyritic texture, regardless of their color. It was later applied to a prized purple porphyritic rock, Imperial Porphyry or Porfido rosso attico, quarried by the Romans from Mons Porphyrites in the Eastern Red Sea hills of Egypt from the first to fifth centuries A.D., and used as a monumental stone in Imperial Rome and Byzantium (Istanbul). It was originally applied to a rare purple dye, Tyrian purple, extracted by the Phoenicians from murex shells.

“Porphyry” is derived from the ancient Greek word porphyra ( πoρϕύρα), or purple. The porphyry deposit name has a long and fascinating etymological history of over 3,000 years.

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