Some accounts refer to this rare diamond as the 'Eugenie Blue' although it is now recognized that there is no evidence of its having been owned by the Empress. Had she owned it, might the Empress Eugenie not have chosen to flee with this valuable gem rather than the diamond which is named after her? However, a French connection does exist because the cutting firm of Atanik Eknayan of Neuilly, Paris cut this heart-shape, weighing 30.82 metric carats and of a rare dark blue colour, in 1909 and 1910. This date raises the question whether the rough stone came from India or Africa.
In 1910 Cartier's purchased the diamond and sold it to an Argentinian woman named Mrs Unzue; it was then set in a lily-of-the-valley corsage. Van Cleef & Arpels acquired the gem in 1953 and exhibited it as the pendant to a necklace valued at $300,000; they sold this item to a European titled family. In 1959 Harry Winston acquired the diamond, selling it five years later, mounted in a ring, to Marjorie Merriweather Post. Finally Mrs Merriweather Post donated the 'Unzue Heart' to the Smithsonian Institution in Washington where it is on display today.