(IDEX Online) - De Beers today announced the delivery of first production from the new underground operation at its Venetia mine, in South Africa.The $2.2bn underground expansion began in 2012, is expected to extend the life of the mine to the mid-2040s and is expected to produce an average of 4.5m carats a year.De Beers describes it as "the biggest single investment in the country's diamond mining industry in decades".Open pit mining at Venetia, in the northern province of Limpopo, ceased in December 2022 after 30 years.Venetia is De Beers' biggest South African mine, representing around 40 per cent of its production in the country.Last week the UK-based miner reported a five per cent drop in its Q2 production, largely because of the planned transition of Venetia from open-pit to underground.De Beers says overall construction of the underground mine, which currently has 4,300 employees, is now 70 per cent complete, with construction and production ramp-up continuing over the next few years.It expects to recover an average of 4.5m carats a year from 6m to 7m tonnes of material mined at depths down to 1,000 meters.Pic courtesy De Beers