Angola has officially started diamond mining at its new Luele project, the biggest in the country and one of the world's largest by estimated resources, it said on Monday, at a time when global diamond demand is already depressed.

Demand for diamond jewellery has been hit by high interest rates in the US, home to 55% of global demand, a muted post-pandemic recovery in China and competition from lab-grown diamonds.

Angola's State-controlled diamond miner Catoca found the Luele diamond deposit at the project, previously known as Luaxe, in 2013 in one of the largest discoveries in the diamond industry in more than half a century.

"This is the only major new diamond mine in the world that will commence production this decade," independent diamond analyst Paul Zimnisky said.

Luele's resources contain an estimated 628-million carats of diamonds with a life-time of 60 years, according to the project's presentation, seen by Reuters.

The presentation did not disclose the project's production plans for 2024. De Beers, the world's largest rough diamond producer by volume, estimates 2022 global rough diamond production at 121-million carats.

The project's plant has an initial annual processing capacity of 4-million metric tons of ore a year with gradual increase to 12-million tons in several years. During the pilot stage, Luele has already mined 5-million carats of diamonds, according to the presentation.

The $600-million project is starting at a challenging time for the industry.

Demand for rough diamonds has been weak in recent months with India - cutter and polisher of 90% of the world's rough diamond - asking the global miners to stop selling it the gemstones to manage accumulated stocks.

"You can't delay opening a mine, but I think it's opening at a terrible time for diamonds," Richard Chetwode, a diamond industry consultant said.

The project, however, could attract additional budget proceeds to the country, which has been battling with high inflation, and support future investment in the country.

"It's fair to say Angola is the most prospective nation for diamonds," Zimnisky said.

"There has definitely been some volatility in industry fundamentals the last four years, but I think most of that is behind us for now. The pandemic, lockdowns, stimulus, and then the unwinding of that was a very unusual circumstance."

Catoca, in which Russia's sanctions-hit Alrosa ALRS.MM owns 41%, currently holds a 50.5% stake in the Luele project. Alrosa's geologists helped to discover the diamond deposit, but it did not get a direct stake in the project.