Recent Research on the Napoléon Diamond Necklace

This historic diamond necklace (Figure 1) was the subject of a recent study which was published in "Gems and Gemology" (Gaillou E., Post J.E., "An examination of the Napoléon Diamond Necklace". Gems and Gemology, vol. 43, no.4, issue Winter 2007). Presented here is a summary of the history of the necklace and the main results obtained during the study.

Figure 2: This painting by Giovan Battista Borghesi (1790–1846) depicts Marie-Louise wearing the diamond necklace. It currently resides in the Galleria Nazionale in Parma, Italy; courtesy of Scala/Art Resource, New York.

History

Napoléon Bonaparte presented this magnificent necklace to his second wife, Marie-Louise, Empress of France, as a gift to celebrate the birth of their son, the emperor of Rome, in 1811 (Figure 2). The necklace was designed and assembled by the jewelry firm Nitot and Sons of Paris and complete in June 1811 for the fee of 376,274 French francs. Following the fall of Napoléon and his exile to Saint Helena in 1815, Marie-Louise returned to her Hapsburg family in Vienna, Austria, with her personal jewels, including the diamond necklace. After her death, the necklace passed to her cousin, Archduchess Sophie, her sister-in-law, who removed two diamonds from the necklace in order to shorten it and put them into earrings, the current whereabouts of which are unknown. Following the Archduchess’s death in 1872, the necklace was inherited by her three surviving sons, one of whom, Charles Louis, later acquired the interests of his two brothers. Charles Louis’s third wife, Maria Theresa, inherited the Napoléon necklace upon his death in 1914.

In 1929, Archduchess Maria Theresa sent the jewel to the United States to be sold. But the agents she chose to sell the necklace were not the persons they claimed to be, i.e. "Colonel Townsend," who had allegedly served in the British Secret Service, and "Princess Baronti," a novelist. In fact, the Townsends' true identities have never been confirmed. The necklace arrived in American at about the same time as the stock market crash, and the Townsends quickly realized that they never would be able to sell the necklace for the $450,000 asking price. The couple engaged Archduke Leopold, Marie-Theresa’s grand-nephew, who was from the ruined branch of the Hapsburg family and who worked in New York as a "sausage sailor man", in order to authenticate the necklace to prospective buyers. The Townsends negotiated deals to sell the necklace several times, and eventually sold it for $60,000 to David Michel, a New York diamond dealer. The Townsends sent $7,270 to Maria Theresa and kept the balance to cover their "expenses related to the sale," which included a reported $20,000 for Archduke Leopold. The affair ultimately went to court, as Maria Theresa had engaged an emissary to retrieve the diamonds and had revoked the Townsends’ authority to sell the necklace. The necklace was returned to Maria Theresa, Archduke Leopold went to jail, and the Townsends took flight and were never seen again.

In 1948 the necklace was sold by the Hapsburg family to French dealer Paul Weiller, then to the New York diamond dealer Harry Winston and finally to Mrs. Marjorie Merriweather Post. In 1962, she gave the necklace, in its original case (Figure 3) to the Smithsonian Institution.

Figure 3: Original box of the Napoléon Diamond Necklace, made in Paris. Photograph by Kenneth Larsen.

The Napoléon necklace contains 234 colorless diamonds, totaling ~263 ct, set in silver and gold, with the largest stone weighting ~10.4 ct. It consists of 28 brilliant oval-cut diamonds from which are suspended a fringe of nine pendeloques, and 10 briolette diamonds. Additionally, there are five small brilliants mounted above five of the pendeloques, and the other four pendeloques are attached to motifs decorated with 23 and 12 brilliants, respectively (Figure 4). Each of the briolettes are set with 12 "roses de Hollande" diamonds.

Figure 4: Details of the Napoléon Diamond Necklace.

The diamonds have never been graded, because they have never been removed from their settings. There are obvious crystalline inclusions in some of the diamonds, mostly what appear to be disc-shaped tension halos around sulfide crystals (Figure 5).

Figure 5: Disc-shaped tension halos, probably around sulfide crystals, as inclusions in one of the diamond.

We examined 101 of the 234 diamonds by infrared spectrometry (Figure 6), as diamonds are classified by this method. This classification separates diamonds with nitrogen impurities (type I) from those without (type II). The classes are further subdivided depending on the nitrogen aggregation for type I (type Ia with aggregated nitrogen present, or Ib with only isolated nitrogen) and if boron is present for type II (type IIa if there is no boron, and type IIb if there is). Our study revealed that the proportion of the rare type IIa diamonds was higher than usual: 13 of the 52 larger diamonds are type IIa (Typically, fewer than 10% of natural diamonds are type II.). The others are the more common type Ia diamonds.

Figure 6: Microscope coupled with an infrared spectrometer used to acquire infrared spectra of diamonds in the Napoleon Necklace.

Type IIa diamonds exhibit characteristic features between crossed polarizers (Figure 7); strain features, "tatami graining", appear as banded and cross-hatched extinction patterns with first order interference colors of gray to blue.

Figure 7: "Tatami graining" in the central drop type IIa diamond.

Viewing the necklace under ultraviolet light reveals a large proportion of fluorescent diamonds, mostly with a blue color (Figure 8). Only a few (7) diamonds exhibit a pinkish-orange fluorescence; these diamonds are also type IIa, and are commonly referred to as Golconda-type diamonds (which usually have a light pink color that is not observed here).

Figure 8: The Napoléon Diamond Necklace under ultraviolet light. The diamonds are labeled as to their type. Most diamonds exhibit a blue fluorescence with various intensities; several diamonds have a pinkish orange luminescence; the rest are non fluorescent. Photograph by Chip Clark, Smithsonian.

Conclusion

In addition to its status as an historic icon, our study of the Napoléon Necklace revealed that it also contains some gemologically interesting diamonds. Infrared spectroscopy indicated that the majority of the primary diamonds in the Napoléon Necklace are of the rare type IIa, and are of a high-quality consistent with the jewel’s imperial pedigree. Apparently, the standards used 200 years ago to select the finest diamonds are similar to those still used today. The necklace is equally spectacular under ultraviolet light, and the diamonds’ luminescence behaviors correlate with their types. The Napoléon Necklace is one of the most spectacular diamond jewelry pieces of its period, and as part of the Smithsonian’s National Gem Collection, it along with its story is preserved for future generations.

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