(IDEX Online) - Alrosa is to sell one of the largest diamonds it has recovered since 2000.It says the 242.31-carat gem-quality stone could fetch well over $2m.The rough stone will be offered for sale at the Russian state-owned miner's 100th auction of large diamonds, which will take place in Dubai on 22 March. Viewings are from 14 to 21 March.Two other notable diamonds- weighing 190.74-carats and 136.21-carats are also being sold.The 242.31-carat stone (pictured) which leads the sale measures 21.7x31.3x41.9 mm and is the largest rough diamond to be offered for sale in Dubai for five years.The opening price is over $2m, though according to Alrosa, expert estimates are far higher.Evgeny Agureev, Alrosa's head of sales, said: "Rough diamonds, which potentially allow for cutting a diamond larger than 100 carats, are extremely rare in nature. "Even less often such gems are traded. According to the law, all rough diamonds larger than 50 carats mined in Russia undergo a state examination for redemption to the state fund."