The case, a masterpiece of early 16th century metal work, was stolen overnight on on Friday from the Thomas-Dobrée museum in the western city of Nantes along with a golden Hindu statue and a collection of golden coins.
It narrowly escaped being melted down after the French Revolution and the theft has sparked outrage over the loss of a work of art seen as of enormous historical value.
“If by any chance the thieves were motivated by the fact that it is shiny and made of gold, they should understand that its historical and symbolic value far outweighs its 100 grams of gold,” Catherine Touchefeu, a departmental councillor.
The case, which has been the property of the Thomas-Dobrée museum since 1886, had been on display in a special glass container in the museum since last Tuesday of last week.
“These burglars have attacked our common heritage,” said Philippe Grosvalet, the president of the Loire-Atlantique department of which Nantes is the capital.
“Much more than merely a symbol, Anne de Bretagne’s heart belongs to our shared history. Queen Anne, Duchess of Brittany, had wished that her heart be buried with her parents,” he said.
Anne was the only woman to have been twice crowned queen of France.
She married Charles VIII of France in 1491 and became queen consort at the age of 12. But he died without an heir in 1498, and she married Louis XII the following year.
She died in 1514 and was buried next to other French royals in the Paris suburb of Saint Denis. But she had asked for her heart to kept in Brittany, and it was taken to rest in her parents’ tomb at the chapel of the Carmelite friars in Nantes.