Imperial Porphyry is arguably the rarest and most historically important stone in the world. It comes from only one source; a single mountain in Egypt that the Romans called Mons Porphyry. It is a purple, volcanic stone, very dense and fine-grained, with small white inclusions.
According to Pliny’s Natural History, Imperial Porphyry was discovered in 14 AD by Caius Cominius Leugas, a Roman legionary. Seeing that this hard stone was the purple color which symbolized Imperial power, he had samples brought to the Emperor Tiberius in Rome. When Tiberius saw that this royal-colored stone was solid enough for building and carving, he decreed that “Imperial Porphyry” would be for the use of the Imperial family only.
Tiberius quickly established a quarry on Mons Porphyry and began to use the stone for the decoration of Imperial palaces and other buildings. Later emperors continued the tradition. Imperial Porphyry was used for panels, floor tiles, statues, sarcophagi, and for the pillars of official buildings throughout the Roman world.
Perhaps most significant was the large circle of Imperial Porphyry in the center of the floor of the Pantheon in Rome. New Emperors stood in this symbolic circle to be crowned for the next 300 years.
This use to convey royalty made Imperial Porphyry truly the stone of Empire, causing it to be more significant and powerful to the Empire than gold.
Imperial Porphyry was the supreme expression of Roman Empire throughout the next few turbulent centuries. Emperors were often raised and deposed quickly. It was easy for a usurper to raise money, gather troops, put on a purple robe and try to take over; but the person who had the resources to import Imperial Porphyry and the means to build with it was the Emperor.
When the Emperor Constantine established Constantinople (now Istanbul) as the new Roman capital in 330 AD, Imperial Porphyry remained the most important stone of Empire. Constantine erected a 30-meter column made from seven huge Imperial Porphyry drums with a statue of himself at the top. The statue was destroyed over time but the pillar itself still stands. Eight Imperial Porphyry pillars still support the niches of the Hagia Sophia, built by the Emperor Justinian.
The Byzantine Emperors used Imperial Porphyry to tile the interiors of some palace rooms, including the room where pregnant empresses gave birth. Young princes were given the title porphyrygenitos to indicate they were legitimate imperial heirs, born and raised in rooms of porphyry.
In 600 AD the Byzantine Empire lost control of Egypt to invading Muslim forces, and the Roman world lost control of the Imperial Porphyry quarry. Now that Roman civilization had no means to obtain new Imperial Porphyry, it became even more precious. Remaining stock was used only for royal palaces and tombs. No new large scale public works were made from Imperial Porphyry, although some buildings included reworked porphyry from earlier Imperial projects.
Constantine XI, the last of the Byzantine emperors, was crowned not in Constantinople, but in the provincial city of Mystras, which had a single Imperial Porphyry tile set into the floor. The new Emperor was said to have stood on that tile to be sworn in in 1449, continuing and ending the tradition that had been part of the Empire for more than 1,400 years.
In later centuries Porphyry remained the supreme symbol of Imperial power. Several Holy Roman Empire monarchs, including Fredrick II, Henry IV and William I, all had tombs of Imperial Porphyry, continuing an Imperial custom which had been first started by Nero in 63 AD.
Centuries later, Napoleon Bonaparte wanted to be buried in an Imperial Porphyry tomb, as a symbol that he was a legitimate heir to the Roman Emperors. He had officials search for the long-lost Imperial quarry during his expedition to Egypt, but was unable to find the ancient source. He was instead buried in a sarcophagus of much more common red porphyry.
The ancient quarry on Mons Porphyry was rediscovered by Sir John Wilkinson, a former president of the Royal Geographic Society in 1823, only two years after Napoleon’s death. The site is now a World Heritage site.