GENEVA (Reuters) — The largest diamond ever cut in Russia, a 100.94 carat stone called the Alrosa Spectacle, will be auctioned in Geneva later this month.

The diamond could fetch between 12 and 18 million Swiss francs ($19.96 million) when it goes under the hammer at Christie’s on May 12.

“This fantastic 100 carat D color diamond was cut from a rough stone that originally weighed more than 200 carats. It was called the Sergei Diaghilev rough diamond and it was mined in 2016,” Marie-Cecile Cisamolo, a specialist in the auction house’s jewelry department, said.

“Between the rough and diamond that we’re offering today, it took one year and eight months to cut into this perfect stone.”

The diamond is one of 144 lots on offer in the sale, which also includes rings, earrings, brooches and other pieces made with diamonds, sapphires and rubies.