The Renard diamond mine, in Quebec, has fully transitioned to underground mining, its new ore sorting plant is operational and the mine is now set for higher processing rates, grades and carat recoveries in the second half of the year.

The transition from openpit operations and the completion of the ore sorting plant, which was installed to improve breakage issues, also mark the end of the principal construction capital spending at Renard, CEO Matt Manson said on Friday, announcing Stornoway’s second-quarter production and sales results.

Renard produced 223 351 ct, from the processing of 562 060 t of ore at an average grade of 40 carats per hundred tonnes (cpht), which is a decrease on the first quarter’s production of 285 851 ct, but in line with the company’s guidance. The grade and carat recoveries reflect the processing of lower-grade production ore and ore stockpiles as the mine transitioned to underground mining.

Second-quarter sales amounted to 202 283 ct, representing run-of-mine production recovered between February and March. Stornoway reported gross proceeds of C$28.6-million, at an average price of $109/ct.

Mining at Renard 3 openpit concluded in April and the ramp-up of underground mine production progressed steadily during the quarter, with mined underground tonnes averaging 3 864 t/d in June.

The new ore sorting plant, which was commissioned in March, is now fully operational and the diamonds recovered since sorting started exhibit low levels of breakage, despite the highly abrasive characteristics of the ore processed through the plant, Stornoway said.

Waste rejected represents between 15% and 30% of material sorted, with 1% to 2% kimberlite content in the reject stream.

“We have been particularly encouraged by the performance of the new ore sorting plant. Initial diamond results are encouraging, and given the volume and quality of the waste that is being rejected we see the potential for processing capacity in our plant beyond its current nameplate rating. Exploiting this potential new capacity will involve the development of a modified mine plan to support the accelerated mining required, and permitting,” Manson said.

Earlier in the week, Stornoway temporarily closed the Renard mine, owing to wildfires in the vicinity.