On December 10, Christie’s London offered a 35.36-carat blue diamond classified by the Gemological Institute of America as "fancy deep grayish blue," the finest shade for a gem of that color. Blue diamonds weighing more than 20 carats are extremely rare in any case — fewer than 10 have been recorded. Not least, the Christie’s piece was enhanced by the aura of history. The catalogue noted that its earlier owners could be traced as far back as 1664, when King Philip IV of Spain presented it to his daughter Margarita Teresa on the occasion of her betrothal to Emperor Leopold I of Austria.

The Christie’s team, however, remained unaware of a detail that reveals its art-historical context, giving a clue to its likely maker and intended recipient, and hugely increases the historical significance of the gem. While the stone comes from India, which supplied the finest diamonds to the Middle East and Europe for centuries, the geometrical pattern of the facets is Iranian. It is reproduced, among other places, in the vaulting design of countless mosque and mausoleum domes from at least the 13th century. For a stone cut prior to 1664, the selection of such a pattern can point to only one gem cutter: the Iranian poet, calligrapher and jeweler Sa’ida-ye Gilani, who moved to India at about age 20, after a fire destroyed the family house in his hometown of Lahijan, in northern Iran. Called in by the Moghul emperor Jahangir (1605-27), he was soon appointed head of the imperial jewelery workshop and was later confirmed in his position by Jahangir’s son Shah Jahan (1627-58).

Famous in his time and mentioned in several historical chronicles and anthologies of Persian poetry, both in Iran and India (where Persian was the language of literature, administration and polished intercourse at all Islamic courts), Sa’ida sank into near oblivion until 2002, when his oeuvre and biography were reconstructed on the evidence of previously untapped Persian sources from Iran and India and from objects he had wrought.

These include a carmine-red spinel. The precious historical stone was presented by Shah Abbas of Iran to Jahangir, who requested that Sa’ida record the event by incising the emperor’s name and titles on the gem. Luckily, the spinel came to light a few years ago, with inscriptions matching those Jahangir records in his memoir. Jahangir describes other precious objects that were entrusted to Sa’ida for him to inscribe. His successor, Shah Jahan, for example, commissioned Sa’ida to direct the construction of an imperial throne studded with gems, a task that took seven years.

It is highly likely that Sa’ida, as head of the imperial jewelery workshop under two emperors who admired his skills, was selected to cut a stone as rare as the blue diamond. The facts concerning Sa’ida were published by this writer (under his scholar’s signature, Assadullah Souren Melikian-Chirvani) as recently as 2002 in volume 13 of the Bulletin of the Asia Institute, an American journal of Iranian and central Asian studies printed in Bloomfield Hills, Michigan. But news from the academic world spreads very slowly.

The blue diamond is the only historical diamond cut by an artist from the Islamic world that has come down to us in its original state as an admirable work of art. The other two famous historical stones, the Koh-i Noor diamond (in Persian, "the Mountain of Light") and the Timur ruby (actually a spinel), both taken out of India in British colonial times, were modified by recutting and polishing. The value of the blue diamond, intact and in its original condition, is thus hugely increased.

Laurence Graff, a world leader in diamonds who responded to the irresistible lure of the stone, stubbornly battled a Russian-born New York professional and won the contest to the tune of £16 million ($24.3 million). Graff now has reason to congratulate himself for having acquired a major if miniature work of art.

The contrast between the performance of the gem and that of the other works in the auction, which were all overrated commercial merchandise, could not have been greater. The sale of the diamond concluded a session in which only 55 percent of the lots found takers.