Famous Diamonds: the Blue Heart Diamond


The name “Blue Heart” seems to have been inspired by the rare deep blue color of the diamond and it’s extraordinarily beautiful heart-shaped cut, that makes it perhaps the world’s prettiest blue diamond. The “Blue Heart” diamond is sometimes known as the “Unzue” diamond, after the Argentinean woman Mrs. Unzue who owned the diamond for 43 years, having purchased it from Cartier’s in 1910, two years after it’s discovery. The diamond is also mistakenly referred to as the “Eugenie Blue,” after Empress Eugenie of France, the empress consort of Napoleon III (1852-1870), but she could never have owned this diamond because it was discovered only in 1908.

The Blue Heart diamond is a 30.62-carat, heart-shaped, brilliant-cut blue diamond. According to the Gemological Institute of America, the Blue Heart Diamond is a natural fancy deep-blue diamond, with a clarity grade of VS-2.

The “Blue Heart Diamond” enjoys the rare distinction of being the largest heart-shaped blue diamond in the world

The “Blue Heart” diamond belonging to the National Gem Collection of the Smithsonian Institution, is the 11th largest blue diamond in the world, according to our list of known famous blue diamonds in the world, arranged in descending order of carat weights. However, this blue diamond with a rare heart-shaped cut, enjoys the rare distinction of being the largest heart-shaped blue diamond in the world, a position which it had held since its cutting in Paris in 1909/1910, a position which may not change in the forseeable future, given the extreme rarity of large blue diamonds, and the rarity of the heart-shaped cut, seldom employed in blue diamonds. Apart from the 30.82-carat Blue Heart diamond, there are only three other heart-shaped blue diamonds in the table given below, an indication of the rarity of this shape. These are the 27.64-carat, “Heart of Eternity” diamond, the largest of 10 extremely rare blue diamonds exhibited at the Millennium Dome in London in the year 2,000 together with the 203.04-carat Millennium Star, the centerpiece of the exhibition; the 13.78-carat heart-shaped Begum-blue diamond; and the 5.46-carat heart-shaped Marie Antoinette blue diamond.


The Blue heart diamond is a rare Type IIb diamond, and all naturally colored blue diamonds belong to this group. However, the occurrence of these diamonds is much less than 0.1 % of all natural diamonds. Type II diamonds are nitrogen-free or contain undetectable quantities of nitrogen.

If the diamonds are not only nitrogen-free but free of all other chemical impurities, they are known as Type IIa, which constitute about 1-2 % of all naturally occurring diamonds. However, instead of nitrogen, if they contain trace quantities of another impurity boron, the diamonds are known as Type IIb. Boron atoms incorporated in the crystal structure of the diamond, changes it’s absorption spectrum imparting the blue color to the diamonds. The diamonds also become semi-conducting, unlike other diamonds which are non-conductors of electricity.

Previously the origin of the Blue Heart diamond was uncertain, and thought to be either India or South Africa, even though by the beginning of the 20th century, most of the historical diamond mines of the Eastern Deccan Plateau in India were already abandoned.

However, this mystery has been solved and more information about the diamond has been unearthed, thanks to the untiring efforts of the dedicated scientists of the Natural History Museum of the Smithsonian Institution, the present owners of the diamond. The researches went into the archives of De Beers, and unearthed evidence to show that the diamond was discovered in the Premier diamond mines of South Africa, in November, 1908, and the rough stone weighed 100.5 carats.

Mistaken reference to “Blue Heart Diamond” as “Eugenie Blue Diamond” corrected after the Smithsonian research

The “Blue Heart” diamond was earlier mistakenly referred to as the “Eugenie Blue” diamond, because of the misconceived notion, that the diamond once belonged, to Empress Eugenie of France, the Empress consort of Napoleon III (1852-1870). However,we now know for certain that Empress Eugenie, who reigned between 1852 and 1870, could never have owned this diamond, because it was discovered only in 1908.

The French Connection to the Blue Heart Diamond

The Blue Heart diamond certainly did not belong to Empress Eugenie of France, but undoubtedly there is a French connection to this diamond, as the rough diamond was cut and polished, and transformed into it’s modern heart-shaped form by the renowned French diamond cutting firm, Atanik Ekyanan of Neuilly, Paris between 1909 and 1910. The cut and polished diamond was sold in 1910 to Cartier’s, who set the diamond in a “Lily of the Valley” corsage and sold it to an Argentinean woman Mrs. Unzue in 1911.

The Blue Heart Diamond is sometimes referred to as the “Unzue Diamond” as the Unzue family owned the diamond, until 1953

The diamond remained in the Unzue family for 42 years and hence the diamond is sometimes referred to as the “Unzue Diamond.” In 1953, it was purchased by the jewelry firm Van Cleef & Arpels, who dismantled the corsage setting, and re-set the diamond in a pendant, surrounded by 25 colorless or white diamonds. The pendant and the accompanying necklace was priced at US$ 300,000, and was sold to an unnamed European titled family.

In 1959, Harry Winston acquired the diamond, and re-set it again in a platinum ring, surrounded by 25 colorless/white, round brilliant-cut diamonds and sold it to Marjorie Merriweather Post, the American socialite and founder of General Foods Inc., in 1960.

Marjorie Merriweather Post generously donates the Blue Heart Diamond in 1964 to National Museum of Natural History of the Smithsonian Institution

The diamond remained with Mrs. Post until the year 1964, when she finally decided to generously donate the rare blue diamond to the National Museum of Natural History of the Smithsonian Institution, at Washington DC, where it is on display in the Janet Annenberg Hooker Hall of Geology, Gems and Minerals.


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