03/04/2026
Imagine being able to handle this incredible diamond regularly! Our good friend Jim Russo did!
A blue diamond weighing over 30 carats is among the rarest gemstones and “The Blue Heart” at 30.62 ct is just that. As a type IIb diamond (with boron as an impurity in very small concentrations, typically in the order of magnitude of 0.01-10 ppm or “parts per million”, roughly meaning that for every million atoms of carbon in the crystal lattice there are up to 10 atoms of boron) it constitutes a very rare geological evidence of the ultra deep reach, more than 800 km, of superficial boron that was brought to those unusual diamond-forming depths by oceanic rocks via subduction during geological orogenic events. Cut near Paris in 1910 from a 100.5 carat strong blue rough found one year earlier at the then called Premier mine in South Africa (now Cullinan mine). It was then set by Cartier on a necklace eventually sold the stone to the Argentinian philanthropist Maria Unzué de Avelar, hence its other alias: the Unzué Heart diamond. After passing through Van Cleef & Arpels as a necklace pendant in 1953, it ended up a few years later at Harry Winston and then set in a platinum ring along with 25 round diamonds. Its last proprietor, Marjorie Merriweather Post, bequeathed it in 1964 to the Smithsonian National Museum of Natural History, in Washington DC, only two months after buying it from Harry Winston.
Photo Chip Clark © Smithsonian National Museum of Natural History
