(IDEX Online) - Rio Tinto today (16 January) announced a 50 per cent drop in its Q4 diamond production at Diavik, Canada's largest diamond mine.It said the closure of two kimberlite pipes - one underground, the other open pit - towards the end of the year had impacted output.Rio Tinto, the world's second-largest metals and mining corporation, reported production at Diavik, its only diamond mine, at 659,000 carats during Q4 2023, down from 1,319 carats in Q4 2022.Production for the full year was 3.34m carats, down 28 per cent on 2022 but still within the company's 3.0m carats to 3.8m carats guidance. Rio Tinto did not provide 2024 guidance in its fourth quarter production results.The company plans to invest $40m in underground mining that will prolong Diavik's life to early 2026. The deposit has produced over 100m carats since commercial production started in 2003.It said exploration at its Falcon Project in Saskatchewan, Canada, was currently in care and maintenance and may be terminated.Rio Tinto became 100 per cent owner of the mine in November 2021, ending a long legal battle with Dominion Diamond Mines over the mine's operating costs and production targets.Pic shows Diavik mine, Canada.