(IDEX Online) - The Reserve Bank of Zimbabwe (RBZ) has stockpiled 300,000 carats of diamonds since new rules were introduced last October, requiring miners to pay half their government royalties in raw minerals.The move, designed to maintain the value of the country's assets by building up a national reserve of precious metals and stones, was introduced by President Emmerson Mnangagwa (pictured).According to the Harare-based Sunday Mail newspaper, the bank currently holds 300,000 carats of diamonds (value not quantified) by Zimbabwe Consolidated Diamond and RioZim-owned Murowa Diamond, and around 350kg of gold, valued at $20m.RBZ governor told the Mail: "The equivalent cash of diamonds in the reserves is difficult to get because there is no universal body that sets prices for diamonds."He said lithium companies, also covered by the new rules, were allowed to submit their royalties in cash because the mineral was too bulky.President Mnangagwa, announcing the rules last October, said: "We cannot, as the present government, and as the current generation, run and manage finite resources profligately, without any regard for generations yet and sure to come."Pic shows Murowa mine