An unusual diamond with another diamond moving freely inside was recently unearthed from a mine in the Sakha Republic (Yakutia), Russia's Siberia. It is the first stone of its kind in recorded history, Russian state mining company Alrosa PJSC said. /VCG Photo

Known as the "Matryoshka" diamond nicknamed for the famed Russian nesting dolls, the diamond is small at just 0.62 carats measuring 4.8 x 4.9 x 2.8 mm. The inner diamond is even tinier at 0.02 carats and 1.9 x 2.1 x 0.6 mm. /VCG Photo

The double diamond thought to be over 800 million years old, and scientists hypothesize that the internal diamond formed first and was then enclosed by the larger crystal later in the formation process. /VCG Photo