The Origin of the Porphyry Deposit Name: From Shellfish, Tyrian Purple Dye, and Imperial Rome to the World’s Largest Copper Deposits

Abstract

Abstract The porphyry deposit name has a long and fascinating etymological history of over 3,000 years. “Porphyry” is derived from the ancient Greek word porphyra (πoρϕύρα), or purple. It was originally applied to a rare purple dye, Tyrian purple, extracted by the Phoenicians from murex shells. 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). The name evolved in the field of igneous petrology to include all rocks with a porphyritic texture, regardless of their color. Mining of the first porphyry copper deposits, which were originally called disseminated or low-grade copper deposits, started in 1905. As a result of the close spatial and genetic relationship to porphyry stocks, they became known as porphyry copper deposits. The term was first used by W. H. 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. It was slow to catch on in the geological literature. 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).