Alrosa has recovered an unusual piece of rough featuring one diamond encased inside another, in a style similar to the traditional Russian nesting doll.
The outer stone weighs 0.62 carats and contains an inner cavity of 6 cubic millimeters in which the internal 0.02-carat diamond can move. After the company identified the ‘matryoshka’ stone during the sorting process at its Nyurba division in Yakutia, it studied it using a variety of methods, including Raman and infrared spectroscopies, as well as X-ray microtomography.
“The most interesting thing for us was to find out how the air space between the inner and outer diamonds was formed,” Oleg Kovalchuk, Alrosa’s deputy director for innovations at the company’s research and development geological enterprise, said last week.
The miner has 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,” Kovalchuk explained. “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.”
The nesting diamond is the first of its kind in history, according to Alrosa.