Stolen in 1792, the French Blue diamond's fate puzzled historians for centuries

Stolen along with the French Crown jewels, this prized blue diamond stayed lost for centuries until the detective work of historians and scientists cracked the case.

Louis XV’s Order of the Golden Fleece was one of the most lavish pieces of jewelry ever made. A replica created in 2010 based on an illustration gives a sense of its majesty. Containing famous stones like the French Blue and the Côte de Bretagne, it was stolen in 1792 and dismantled. Many of its components were lost, but the fate of others is known: The Côte de Bretagne was recovered and is held at the Louvre, and the French Blue is known today as the Hope Diamond.
MANUEL COHEN/AURIMAGES

Known by awed gemologists simply as “the Blue,” the world’s biggest blue diamond first vanished in a jewel heist during the turmoil of revolutionary Paris in 1792. Since then, it has resurfaced and disappeared several times around Europe and across the Atlantic. Historians and jewelers have finally ended this treasure hunt that lasted more than two centuries.

Most diamonds are prized for colorlessness, but this remarkable gem stood out for its distinctive deep blue hue. Discovered in India and brought to France in the 17th century, the stone measured a whopping 115 carats—a rare heavyweight in gemological terms.

The diamond came to the attention of France’s Louis XIV, who bought it in 1668. To craft a fitting symbol for the Sun King, Louis had it cut, reducing it to 69 carats but intensifying its brilliance. He had it mounted in a distinctive gold setting that created a sunburst effect reflected in the stone. His great-grandson Louis XV had “le Bleu” set into an elaborate insignia of the Order of the Golden Fleece, a Catholic chivalric order, around 1749.

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