August 23, 2014
Imperial Red Porphyry was first discovered in Egypt in the year 18 CE by the Roman legionnaire, Caius Cominius Leugas. Porphyries are reasonably common, but the rock from which this sculpture was carved, Imperial Red Porphyry, is rare, valuable and has historic significance. The stone came from the quarry of Mons Porpyritis (Egypt), the only source of Imperial Red Porphyry in the world. Stones were carried by oxcart along what was known as The Porphyry Road to the Nile River and then shipped to Rome. Romans valued the stone for carvings. They even used it in the statues and inlaid panels of the Pantheon.
Porphyry is an igneous rock containing both large and fine-grained crystals. The large crystals formed though the slow cooling of magma deep underground. Smaller crystals formed as the magma approached the surface and cooled more quickly. Porphyry is very hard and dense, making it quite resilient and difficult to carve. The sculptor would need great skill, very hard steel tools and much more time than with marble carvings. Imperial Red Porphyry was a mark of great wealth and power.
The photo above is a close-up of the carving on the sarcophagus of St. Helen, the mother of Constantine the Great. It's located in the Vatican Museum in Rome.
Photo details: Camera Maker: Apple; Camera Model: iPhone 5s; Focal Length: 4.1mm (35mm equivalent: 30mm); Aperture: f/2.2; Exposure Time: 0.050 s (1/20); ISO equiv: 320.