When asked what had caused the monarchy of France to collapse Napoleon listed three reasons, one was the "Affair of the Diamond Necklace"
The infamous necklace was 2800 carats. First was a choker of seventeen diamonds, five to eight carats each; from that hung a three-wreathed festoon and pendants; then came the necklace proper, a double row of diamonds cumulating in an eleven-carat stone, finally, hanging from the necklace four knotted tassel. It originally was tied with pink satin ribbons which was Du Barry's favorite color, but later changed to blue ribbons. It cost 1,600,000 lives. Perhaps in today's currency, this is the equivalent of $100 million. The jeweller Charles Bohmer had the beautiful necklace made for Madame du Barry. But Louis XV died, du Barry was banished from court, and Bohmer placed his hopes on the new Queen to purchase the necklace, but Marie Antoinette would not purchase it or even permit Louis to buy it as a gift for her. When the Jeweler mentioned he would be ruined if he couldn't sell it, Marie told him to sell the individual gems.
In 1785 the ambitious Cardinal de Rohan fell into the clutches of a confidence trickster called Jeanne de la Motte. Having lost favour years before, the worldly prelate was desperately seeking a means of regaining the good graces of the Queen. Jeanne convinced him that Marie Antoinette wanted him to purchase for her a fabulous necklace made of 647 diamonds. The gullible cardinal proceeded to acquire the necklace, believing he was acting on behalf of his Queen. Jeanne took charge of the diamonds as the Queen's "go-between", and her husband smuggled them off to England to be sold. When the expected payment for the necklace failed to materialise, the jeweller took his claim directly to the Queen in Versailles.
Marie Antoinette was horrified. She saw in it a plot to bring further discredit upon her and she demanded that the Cardinal de Rohan be made to stand trial. Although Jeanne de la Motte was convicted, the cardinal was acquitted by the Parlement of Paris. This was openly celebrated as a victory over the "Austrian woman", because most people believed that the extravagant and unpopular Queen simply must be behind the matter somehow or other.
To see the necklace as portrayed in the movies and history, follow the link below.
To see some of Marie Antoinette's surviving jewelry Follow the link below.