(IDEX Online) - Petra Diamonds reported a 44 per cent drop in revenue for FY2023 as recoveries and sales fell, especially among exceptional stones.The UK-based miner is closing its loss-making Koffiefontein mine, in South Africa, but says it's ahead of schedule to re-open Williamson, in Tanzania, after the breach of a tailings dam last October.It also reports operational turnarounds at its Cullinan and Finsch mines, in South Africa, which should allow it to improve grades and says it remains on track to deliver strong production growth. Total revenue for FY2023 was $328.4m, down 44 per cent on $584.1m in FY2022. The contribution from exceptional stones was 12.6m, down almost 86 per cent from $89.1m.The overall number of carats sold was down 34 per cent from 3,536,316 to 2,339,662.Petra CEO Richard Duffy said: "As previously announced, our strong balance sheet and flexible sales process enabled us to postpone the majority of our Tender 6 rough diamond sales into FY 2024 on the back of what we believe to be a temporary slowdown in demand for rough diamonds."We continue to expect a supportive diamond market in the medium to longer term as a result of the structural supply deficit, which will benefit our strong growth profile."Pic shows Cullinan mine