About five weeks ago, Alrosa surprised its Instagram followers with a video that seemed to show a tiny rough diamond rattling around in the cavity of a larger one. The caption read, "A diamond in a diamond? We couldn't help but share this very special find with you."

At the time, Alrosa wasn't quite sure what to make of the phenomenon. Nobody at the mining company had ever seen anything like it.

Despite weighing just 0.62 carats, the tiny specimen became the focus of a series of elaborate tests to determine exactly what it was.

"We are not sure if the smaller one is a diamond," Alrosa wrote in the Instagram caption. "Our scientists are looking forward to studying the crystal. It will be researched with non-destructive methods."

Alrosa is now reporting that by utilizing Raman spectroscopy, infrared spectroscopy and X-ray microtomography, its researchers are able to confirm that both the smaller crystal and its host are diamonds.

The larger one measures 4.8 mm x 4.9 mm x 2.8 mm, while the smaller, tabular-shaped crystal weighs .02 carats and measures 1.9 mm × 2.1 mm × 0.6 mm.

Alrosa is calling the curious double-diamond "Matryoshka," which is a nod to the popular Russian nesting dolls. The diamond was discovered in Yakutia at the Nyurba mining and processing division of Alrosa.

Explaining the extreme rarity of this find, Oleg Kovalchuk, deputy director for innovations at Alrosa's Research and Development Geological Enterprise, said, "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."

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

Alrosa's scientists believe there was an internal diamond at first, and the external one was formed during the subsequent stages of growth.

Please check out Alrosa's video here...