Known as the Grand Condé, the pear-shaped diamond was stolen during an overnight raid on the château in October 1926. The thieves concealed the diamond inside a hollowed-out apple; however, it was recovered weeks later after a hungry maid at their hotel bit into the fruit.
The diamond is going on display at the Condé Museum for the first time since the theft, with the exhibition running until 3 January. Museum director Mathieu Deldicque told BBC News that the extraordinary apple story, while seemingly far-fetched, was widely reported in newspapers at the time.
The exhibition comes amid heightened concern over security at European cultural institutions, following a series of high-profile heists, including the daylight theft of jewellery from the Louvre in Paris.
Deldicque declined to disclose the diamond’s insured value to CNN; however, he said extensive academic analysis had established identifying characteristics unique to the stone.
The exhibition will also feature the results of that research, alongside previously unseen archival material documenting the diamond’s history and theft. The Grand Condé’s origins remain uncertain. The stone was first recorded in 1740 in an inventory of Louis Henri de Bourbon, Prince of Condé, following his death.
It later entered the collection of Queen Marie-Amélie of Bourbon-Sicily, wife of French King Louis Philippe I, before passing to her son, Henri of Orléans, Duke of Aumale.
The duke bequeathed the diamond to the Institut de France, which owns the Château de Chantilly, located about 50 kilometres north of Paris, along with the thousands of artworks and manuscripts that form the Musée Condé collection.
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