Diamond Necklace, THE, a wonderful piece of jewelry, made in Paris about the year 1775, and intended for Madame Dubarry, the favourite of Louis XV. She, however, was excluded from court on the death of Louis (1774), before the necklace was finished. After being made, this beautiful ornament, adorned with 500 diamonds, was found to be so costly that no one could purchase it. It was valued at 1,800,000 livres, equal to about £80,000 of modern money.
The Prince Cardinal de Rohan, a wealthy, vain, and profligate man, persuaded by an adventuress named De Lamotte, who waited about court, that the queen (Marie Antoinette) regarded him with favour, became completely infatuated with the idea. One night in August 1784 the poor dupe had the happiness of a moment's interview in the groves around Versailles with the queen in the person of a girl who closely resembled her. De Lamotte had stated to the cardinal that the queen was desirous of obtaining this glorious necklace, and that not having sufficient money just then, she would sign an agreement to purchase it if the cardinal would become security. The cardinal consented. The agreement was approved of and signed with the royal signature, as also with that of the cardinal, who, on the 1st February 1785, carried off the treasure from the maker to Versailles, where it had been agreed the queen should send for it. In a few days De Lamotte and her husband, having disappeared from Paris, were busily engaged in selling the separate diamonds in the necklace. The whole transaction had been a trick; the messages from the queen, oral and written, were without foundation, the latter, indeed, being forged by a soi-disant valet, who was skilled in imitating handwriting. The plot was discovered by means of the maker of the diamond necklace, who, not receiving any money when the period of the first instalment had arrived, went to court, demanding to know if the necklace had been delivered to the queen. In a few months the cardinal found himself in the Bastille, where some of those by whom he had been duped had already been lodged. In May 1786 the trial of the prisoners was brought to a close. De Lamotte was branded on each shoulder with the letter V (for voleuse, 'thief'), and was sentenced to perpetual imprisonment. Her husband, who had fled to England, was sentenced in his absence to the galleys for life. The cardinal and the girl who had personated the queen were dismissed without punishment. The queen was falsely supposed by the populace of Paris to have had a part in the plot, and the odium resulting from it was heaped upon her, even at the last, when she sat on the tumbril that bore her through a raging and cursing mob to the guillotine.
See Carlyle's study, in his Essays: Vitzel's Story of the Diamond Necklace (new ed. 1880); and French works by Campardon (1863) and D'est Ange (1889).