(IDEX Online) - Alrosa reported its second-highest monthly sales of rough and polished diamonds in June, as demand for rough stones remained strong.But the Russian state-owned miner warned that the rough market was entering "a long period of supply deficit" as demand remained high, rough diamond stocks at the Indian mid-stream segment were low and miners' rough stocks hit a rock bottom levels.The overall figure of $410m for June - comprising $374m rough and $36m polished - was the highest since January ($430m)."Like for like price index for rough diamonds has significantly recovered year-to-date to pre-COVID level," said deputy CEO Evgeny Agureev. "We see a limited risk of any meaningful supply response from the miners' side." Polished sales were boosted significantly by the 100.94-carat Alrosa Spectacle (pictured), which sold for $14.2m at Christie's Geneva.The emerald cut D-color, IF-clarity, Type IIa gem was recovered from the Zarnitsa kimberlite pipe in the Sakha Republic (Yakutia) and was the largest polished diamond ever cut in Russia.Total monthly sales in June 2020, in the depths of the global pandemic, were just $31.3m.