RAPAPORT... Alrosa will auction a 242.31-carat diamond in Dubai later this month, one of the largest gem-quality rough stones the Russian miner has unearthed in the past decade, it said Friday. The opening price will be in excess of $2 million.The March 22 sale will mark Alrosa's 100th large-diamond auction. The company rarely trades Russian-mined rough diamonds of this magnitude - those that can produce a 100-carat polished stone or larger - because the law grants the state the right to examine and buy them."Even when it is possible to put them on sale on the market, we prefer to cut and polish the diamond[s] in-house," said Evgeny Agureev, Alrosa's head of sales. "Thus, today we are especially pleased to present this exceptional lot as part of our 100th international auction."Viewings will take place at Alrosa's sales office in Dubai from March 14 to 21. Rough diamonds weighing 190.74 and 136.21 carats will also be available, as will several other stones above 10.8 carats.Image: The 242-carat rough diamond. (Alrosa)