JOHANNESBURG  New mining in Zimbabwe has quickly yielded millions of carats of diamonds and could help catapult the nation into the ranks of the world’s top diamond producers, according to the head of a group of experts for the United Nations-backed effort to stop the trade in conflict diamonds.

But the new wealth has provoked fears that the riches will be used to subvert attempts to bring democracy to a country that has long suffered under authoritarian rule, and also to finance conflicts.

“This is a world-class deposit, no doubt about it,” said the expert, Mark Van Bockstael. He described the concentrations of diamonds in the Marange fields in eastern Zimbabwe as among the highest in the world: “The deposit is a freak of nature.”

Other experts agree it is an important find, while awaiting more data to gauge its full magnitude. But the steady accumulation of stones has already emboldened President Robert Mugabe, 86, to consolidate control over the Marange fields to prolong his 30-year grip on power, members of his inner circle said.