<img class="styles__noscript__2rw2y" src="https://s.w-x.co/util/image/w/in-diamond_within_diamond.jpg?v=at&w=485&h=273" srcset="https://s.w-x.co/util/image/w/in-diamond_within_diamond.jpg?v=at&w=485&h=273 400w, https://s.w-x.co/util/image/w/in-diamond_within_diamond.jpg?v=ap&w=980&h=551 800w" > Diamond within a diamond. (Credits: IANS/Alrosa PJSC)

A diamond containing another, free-moving gem inside unearthed from a mine in Siberia is the first stone of its kind in recorded history, Russian state mining company Alrosa PJSC said on Friday.

The diamond may be more than 800 million years old, Alrosa said in a statement.

Dubbed the Matryoshka diamond in reference to the Russian nesting dolls of that name, the stone weighs 0.62 carats, while the internal gem weighs 0.02 carats, the Efe news reported.

"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," Oleg Kovalchuk, deputy director for innovations at ALROSA's Research and Development Geological Enterprise, said.

The diamond came out of the Nyurba mine in the Siberian region of Yakutia, but it was sorters at the Yakutsk Diamond Trade Enterprise who discovered the nature of the stone and passed it on to the Research and Development Geological Enterprise for analysis.

Scientists examined the stone using several different methods of spectroscopy, along with 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," Alrosa said.

"The most interesting thing for us was to find out how the air space between the inner and outer diamonds was formed," Kovalchuk said.

While the scientists have to decide on the exact mechanism, with the existence of a dissolved zone, "one diamond began to move freely inside another on the principle of Matryoshka nesting doll," he said.

An Alrosa spokesman said the company plans to send the Matryoshka diamond to the Gemological Institute of America for further analysis.