One of the most spectacular all-diamond pieces of jewelry in the Smithsonian Insitution is the Napoleon necklace. Thought to have originally been owned by Catherine the Great of Russia, it was presented by the Emperor Napoleon of France to his second wife, Marie-Louise of Austria on the birth of their son in 1811. The silver and gold set necklace contains172 diamonds weighing 275 carats - 28 oval and cushion-cut diamonds, dangling 19 briolette-cut oval and pear shaped diamonds and accented by small, round diamonds and diamond set motifs in a silver and gold setting. The diamonds are cut in "old mine" style, the precursor to the modern brilliant cut, and have a high degree of fire (flashes of color as the stone moves in light), but less brilliance due to less light refraction through the top of the stone.

The necklace has an estimated total gem weight of 275 carats, and the largest single diamond on it weighs approximately 10 carats. When Marie-Louise died in 1847, the necklace was given to her sister-in-law, Archduchess Sophie of Austria, who removed two stones to shorten the necklace. Earrings were made with the two removed stones, the whereabouts of which are unknown.

In 1872, the necklace was bequeathed to the Archduchess' son, Archduke Karl Ludwig of Austria. In 1948, Archduke Ludwig's grandson, Prince Franz Joseph of Liechtenstein, sold the necklace to a French collector who then sold it to Harry Winston in 1960. Marjorie Merriweather Post obtained the necklace from Winston and donated it to the Smithsonian Institution in 1962.

It's difficult to value a piece like this in today's market. However, in 1993, the auction house Christie's in Geneva sold another necklace that Napoleon had given to Marie-Louise that was composed of rubies and diamonds. This necklace sold for $13 million.