STEP INTO THE SOUTH KENSINGTON DRAWING ROOM of London author, collector and decorative arts authority Philip Hewat-Jaboor, and you've entered the inner sanctum of some mythical Egyptian temple. The room is a veritable homage to the splendors of porphyry, a purplish stone flecked with milky-white quartz crystals revered by pharoahs and emperors and used distinctively through the ages in sculpture and decoration. "The phrase 'born to the purple' is supposedly derived from a porphyry-lined chamber in which Emperor Constantine was born," Hewat-Jaboor notes. Indeed, his own walls are lined with giant blocks of faux purple stone, each scored and painted separately by decorative artist Simon Brady. Even the incised grooves between the fictive masonry slabs cast a convincing shadow.

The trompe l'oeil serves as a backdrop to the porphyry objects Hewat-Jaboor has been collecting for 15 years, buying at auction and from leading Paris dealers such as Didier Aaron and Jacques and Patrick Perrin. Among his most prized possessions are a massive 17th-century Italian porphyry mortar, a late 17th-century lidded vase with twin handles, an 18th-century tazza that once belonged to King George IV and a Louis XVI gilt-bronze mounted porphyry cache-pot from Saint-Cloud. On the terrace off an adjoining library, an heroic porphyry kouros figure by contemporary British sculptor Stephen Cox reclines majestically on a marble plinth.

As Carlos Picon, curator in charge of the department of Greek and Roman art at the Metropolitan Museum of Art in New York, puts it, "Porphyry is the noblest of ancient stones, and when artifacts are good, they seem divine." The grainy, igneous rock was first quarried in the upper reaches of the Mons Porphirites, east of the Nile, circa 400-300 b.c. It was regarded as royal and seldom used by the Egyptians. The Romans launched lapidary expeditions into Egypt in 19 a.d., reserving porphyry for imperial use. Its purple color was associated with power and its rarity and durability made it desirable for the effigies of emperors and gods, not to mention the majestic columns, revetment s labs, urns, amphora and tubs of the ruling family.

Around six years ago, Hewat-Jaboor and a few friends undertook a pilgrimage to the abandoned Mons Porphirites mine. The collector recalls the event with a mixture of awe and wonder. "The area was completelyoff-limits—no water, greenery, nor insects in sight, and not a sound to be heard," he says. "Suddenly an amphitheater of purple mountains loomed in the distance, and we ascended an old Roman road on foot, passing fragments, broken columns, the remains of a cistern and crumbling porphyry-block walls along the way. The overall scale and sense of isolation was overwhelming," he says.

The original quarries were abandoned sometime between 350 and 450 a.d., and not until the izth century was porphyry used again in earnest. Italian cosmati, or marble workers, incorporated into their work the architectural fragments they found in the archaeological landscape of Rome. Thus ancient slabs and ruined column shafts were sawed, ground and combined with porphyry fragments and other marbles to create new architectural struc­tures and mosaic pavements.

During the Renaissance, porphyry was gradually adapted to Christian imagery, used to signify the sacrificial blood of Christ and those who died in his name. For instance, the Martyrdom of Saint Lawrence, a mural by Agnolo Bronzino at the Florentine church San Lorenzo, depicts the saint embracing a gruesome death on a fiery grate while a woman at his side symbolically embraces a broken column of porphyry. The seemingly indestructible stone is also associated with immortality. In the Vatican museums in Rome, Saint Helen and Saint Constantia lie in porphyry sarcophagi. More figurative and sculptural work slowly emerged, as new methods of working the ultra-hard, fire-resistant stone were developed. In 16th-century Florence, for example, copper-cutting wheels embedded with diamond-chip abrasives, hydraulic saws and steel drills were used to carve porphyry. The dense stone did not lend itself to crisp detail, however. Instead the allure of historical and religious figures and dynastic portraits of the Medici dukes resided largely in their fluid shape and drapery, vigorous model­ing and lustrous sheen when polished.

"The beauty of Renaissance porphyry work lies in the inherent qualities of the material," says Andrew Butterfield, a specialist in Renaissance and Baroque sculpture at Salander-O'Reilly Galleries in New York. Butterfield explains that these qualities were behind the lexpurpurea, an ancient Roman law that forbade anyone but the imperial family to use porphyry in works of art. "Legal privilege passed to emperors and popes during the Middle Ages," Butterfield continues, "and by the 15th century the Medici were granted similar entitlement."

The most notable porphyry sculptor in Renaissance Florence was Francesco Ferrucci del Tadda, who worked the stone with his signature picchierelli, tiny steel hammers sharpened to fine points. His best-known works in porphyry includeio oval bas-relief portraits of the Medici family and busts of Alexander the Great and Julius Caesar. A towering figure of Justice combin­ing six enormous slabs of stone was begun in 1569 and took the sculptor and his sons more than a decade to complete. It stands in the Piazza Santa Trinita in Florence. An oval porphyry portrait of Grand Duke Cosimo I by Tadda is in the Victoria & Albert Museum in London; his porphyry-on-serpentine depiction of the Head of Christ is in the National Gallery in Prague.

After porphyritic rock was unearthed in Alvaden, Sweden, around 1730, that area became the source for the extravagant objets created for such personages as Marie-Antoinette. The enterprise was purchased by Charles XIV of Sweden, and a great deal of Swedish porphyry was distributed throughout Europe as diplomatic presents. Although the site was sold in 1856, it con­tinued to supply Europe with porphyry until a fire destroyed it a decade later.

For connoisseurs like Hewat-Jaboor, the Swedish variety—which comes in sev­eral colors, including green and earthen brown—lacks the mesmerizing qualities and powerful associations of the purple Egyptian stone. "Swedish porphyry is a completely different animal," says Hewat-Jaboor, and much less sought after by collectors. William Strafford, Christie's head of European furniture and decorative arts in New York, agrees. "Swedish porphyry lacks the romance of Egyptian or Renaissance stone," he says, citing recent auction results at Christie's London to prove his point: "Last December a pair of Louis xvi ormolu-mounted Egyptian porphyry covered urns fetched £78,000 [$122,ooo], while a pair of Swedish porphyry urns fetched a mere £12,ooo [$19,000] pounds."

In porphyry as in much exquisite decoration, it seems, the ancients had the first word—and the last.