Napoléon Bonaparte gave an extraordinary diamond necklace to his empress, Marie-Louise, in 1811. Its intriguing history involves both royals and con artists (and one individual who was both), and it was ultimately donated to the Smithsonian Institution in 1962. Infrared absorption analysis of 101 stones in the necklace revealed that a high proportion of the larger diamonds are the relatively rare type IIa; most of the smaller stones are type IaAB. The luminescence behavior of the diamonds to ultraviolet exposure correlates with their diamond types.
