India-based VD Global discovered the 0.329-carat, D-color, type IaAB diamond, named the Beating Heart, in October, and returned it to De Beers for testing, the miner said last week. The stone originated from one of De Beers’ mines in Botswana, Canada, Namibia or South Africa.

The miner sent the stone to the De Beers Institute of Diamonds, which performed a preliminary analysis, as well as optical and scanning electron microscopy (SEM), infrared spectroscopy and fluorescence, and phosphorescence imaging.

The cavity likely formed because of high-quality inner and outer layers of the diamond that sandwiched a low-quality intermediate layer, the institute posited. The middle part disappeared at some point between its formation and reaching the surface of the Earth. Only the better material “survived,” creating a separate diamond that can move freely inside the external shell.

“I have certainly never seen anything like the Beating Heart during my last 30 years in the diamond sector,” said Samantha Sibley, technical educator at De Beers Group Ignite, the miner’s innovation unit.

De Beers does not intend to cut and polish the stone, and will instead keep it for research and educational purposes, it explained.

The stone is not the first of its kind. In 2019, Alrosa discovered the Matryoshka diamond, named for its resemblance to the famous Russian nesting dolls. That had an outer diamond of 0.62 carats, with a free-moving inner stone weighing 0.02 carats.

“The Beating Heart is a remarkable example of what can happen on the natural-diamond journey from formation to discovery,” said Jamie Clark, head of global operations at De Beers Institute of Diamonds. “A find like this demonstrates why natural-diamond formation and origin is such a fascinating area of study and why it is important to strive for advancements in testing and analysis that can contribute to our knowledge of natural-diamond growth.”