(IDEX Online) - Lucara has extended its "groundbreaking partnership" with HB Antwerp to sell its specials (+10.8-cts) for the next 10 years.The Canadian miner first joined forces with HB in July 2020 to sell the high-value rough from its Karowe mine, in Botswana (pictured).Under the agreement, Lucara's +10.8 carat production is sold at prices based on the estimated polished outcome of each diamond, determined through state-of-the-art scanning and planning technology.A true-up is paid to adjust for any difference between the estimate and the actual price paid, less a fee and the cost of manufacturing.The +10.8 carat rough diamonds have historically accounted for approximately up to 70 per cent of Lucara's annual revenues. Lucara says the deal means higher prices at tender, regular cash flow, and a more efficient supply chain as well as tax benefits and beneficiation opportunities for the Botswana government.Eira Thomas, Lucara's CEO, said: "For the first time in our 10-year history, we have insight on what becomes of each and every +10.8 carat rough diamond produced from our mine, participating in each step of the planning and manufacturing process right through to the final polished sale."