Russian state mining company Alrosa PJSC recently said they had discovered "an unusual diamond with another diamond moving freely inside". The discovery was in Yakutia at the Nyurba mining and processing division of ALROSA.
The company stated in a press release that the stone resembles a traditional Russian Matryoshka doll and is historic since it is a first such diamond in the history of global diamond mining. Comparing the structure of the diamond, the firm stated that internal cavity volume is 6 cubic mm and the internal crystal volume is 1.6 cubic mm with an estimated weight of 0.02 carats (0.004 grams). The inner diamond has a tabular shape and dimensions of 1.9×2.1×0.6 mm. The diamond was discovered during a sorting process, who then handed it over to the Research and Development Geological Enterprise of ALROSA. The R&D department at the firm then analyzed the diamond via various methods to understand the core and the formation of the diamond. They arrived at the conclusion that it was an internal diamond at first, and the external one was formed during the subsequent stages of growth.
Oleg Kovalchuk, Deputy Director for innovations at ALROSA's Research and Development Geological Enterprise said, "The most interesting thing for us was to find out how the air space between the inner and outer diamonds was formed. We have two main hypotheses. According to the first version, a mantle mineral captured a diamond during its growth, and later it was dissolved in the Earth's surface. According to the second version, a layer of porous polycrystalline diamond substance was formed inside the diamond because of ultra-fast growth, and more aggressive mantle processes subsequently dissolved it. Due to the presence of the dissolved zone, one diamond began to move freely inside another on the principle of a matryoshka nesting doll. As far as we know, there were no such diamonds in the history of global diamond mining yet. This is really a unique creation of nature, especially since nature does not like emptiness. Usually, some minerals are replaced by others without cavity formation."