VANCOUVER (miningweekly.com) – Borehole water quality and the excessively suspensive properties of the extremely fine kimberlitic clay materials of the Krone-Endora at Venetia project, in South Africa, have conspired to constrain the improved potential throughput, reported project owner Diamcor Mining of Kelowna, in British Columbia, on Tuesday.
The testing, commissioning and calibration of the facilities at the project continued during the quarter, with an emphasis on refining the project's newly expanded facilities to increase processing volumes, increasing the efficiencies of the screening of material at the project's in-field dry-screening plant, and improving the recovery of water from the project's settling dams.
Both of the project's processing plants are now complete and capable of processing material at significantly higher volumes; however, insufficient recoveries of water from the project's settling dams limited the company's ability to operate these plants at their designed capacities during the period.
Aware of the issue, Diamcor advised that it had in the past spent significant resources removing a large amount of the fine material, and the current issue is a result of the additional fines that are created when water is introduced at the project's main treatment plant.
Diamcor reported that third-party testing and initial modelling have indicated that the challenge can be alleviated through water treatment and paste-thickening solutions. The company said that, while it is now finalising plans to implement a permanent solution, it has added a further screening circuit at the in-field dry-screening facilities, with the aim of further liberating and removing additional fine materials under 1 mm before their delivery to the project's main treatment plant.
Diamcor is also installing automated water-control valves to lower overall water consumption until the water treatment and paste-thickening solution can be finalised.
Meanwhile, the company reported the results of the tender and sale of rough diamonds for the period ended September 30.
During the period, Diamcor sold 7 771.13 ct of rough diamonds for gross proceeds of $1.33-million, resulting in an average price of $171.70/ct, somewhat below the average price for the second quarter of $222.52/ct. Given the continued price weaknesses in certain categories of rough diamonds during the period, Diamcor said it was pleased with the average dollar price per carat achieved, which is indicative of the overall quality of the project's rough diamonds.
At the end of September, the company held 2 465 ct in inventory, before acid washing.
Diamcor said the project continued to demonstrate potential for the recovery of larger rough diamonds, despite limited processing, with three individual rough diamonds in the specials category (+10.8 ct), and 35 individual rough diamonds over 5 ct in size recovered and sold during the quarter.
Diamcor has not yet declared commercial production at Krone-Endora at Venetia, nor has it formalised a production decision, saying recoveries are incidental to the ongoing commissioning and testing exercises performed at the project, which is located directly next to diamond major De Beers’ Venetia mine – South Africa’s largest diamond mine.