VANCOUVER (miningweekly.com) – The company that has discovered the world’s second-largest diamond at 1 109 ct has completed plant upgrades to process material of up to 90 mm in size – the same size fraction as the 3 106 ct Cullinan Diamond, recovered in South Africa in 1905.

Vancouver-based Lucara Diamond Corp, which operates the Karowe mine, in Botswana, has completed the first stage of plant modifications to upgrade the large diamond recovery (LDR) circuit, enabling the processing of large material, it announced Monday.

"The Karowe mine has continued to produce large exceptional high-value stones. The ongoing sale of these diamonds has solidified the company's market leadership position and brand recognition for the sale of exceptional high-quality, large diamonds,” president and CEO William Lamb stated Monday, when announcing the date for the company’s second exceptional stone tender of the year.

Viewings for the tender will take place from November 7 to November 16, with the sale closing at 4:00 pm CET on November 16. The sale will include no fewer than 12 exceptional diamonds, with a combined weight of about 1 100 ct.

“Our focus on advancing our recovery techniques, marketing strategy and the routes to market for the sale of such exceptional diamonds has resulted in the expansion of our premium customer base and is achieving maximum diamond recoveries, prices and shareholder value,” Lamb added.

Lucara has been investing in its plant, having announced in August that it would invest $30-million to install four more X-ray transmission (XRT) diamond recovery units at Karowe to process finer-size fractions. The new units, along with associated conveying and screening infrastructure, will target the recovery of diamonds in the 4 mm to 8 mm size range.

Large diamond recovery XRT units were used in the recovery of the 1 109 ct Lesedi la Rona at Karowe in November last year.