Unusual discovery: Alrosa finds 'diamond within a diamond'

Russian miner Alrosa has discovered what believes to be a first in the history of global diamond mining: a diamond with another diamond moving freely inside it.

The unusual stone, which resembles a traditional Russian Matryoshka doll, was mined in Yakutia, Russia.

Citing scientists, Alrosa said in a media statement that the diamond could be more than 800-million years old.

Despite its complex structure, it weighs only 0.62 ct (0.124 g) and has maximum dimensions of 4.8 mm by 4.9 mm by 2.8 mm. The internal cavity volume is 6 mm3 and the internal crystal volume is 1.6 mm3 with an estimated weight of 0.02 ct. The inner diamond has a tabular shape and dimensions of 1.9 mm by 2.1 mm by 0.6 mm.

The Research and Development Geological Enterprise of Alrosa studied the diamond, using several methods, including Raman and infrared spectroscopies, as well as X-ray microtomography. Based on the results of the study, the scientists made a hypothesis about how the crystal was formed. According to them, there was an internal diamond at first, and the external one was formed during the subsequent stages of growth.   

"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 matryoshka nesting doll," Alrosa Research and Development Geological Enterprise deputy director for innovation, Oleg Kovalchuk said.

“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."