Lace mine on schedule for mid-year start-up
JOHANNESBURG (miningweekly.com) – The Lace diamond mine, in the Free State, was on track for mining operations to start in the second half of this year, Southern African diamond development and exploration company DiamondCorp reiterated on Thursday.
In a project update, the dual-listed company noted that it had now drilled 3 321 m in 21 holes at its 74%-owned mine, which had delineated 2.6-million tonnes of high-grade kimberlite above the 370 m level, an increase of more than two-million tonnes over the original geological model.
Data from bulk testing was scheduled to be completed by the end of the second quarter, while processing of K6 kimberlite, recovered from the production level drives, had started. A 19.83 ct clear white gem diamond had been recovered – the largest gem diamond recovered from underground development to date.
Meanwhile, DiamondCorp pointed out that mine development costs were averaging R38 961/m, higher than the budgeted R37 000/m, as a result of increased operating costs on the company’s underground mining fleet.
“In particular, dump truck breakdowns and repairs have been high owing to the long haul distances from the UK4 Block development levels to surface,” the diamond miner said.
DiamondCorp would, therefore, prioritise the completion of the tunnels and an underground loading chamber required for commissioning of the underground conveyor belt system.
The system, which would handle kimberlite and development waste, was 91% fabricated and on site, 51% installed and on schedule for commissioning ahead of the mining ramp-up.
The conveyor belt was capable of bringing 400 t/h to surface – averaging 8 000 t/d – compared with the maximum of 975 t/d currently being hauled by the company’s five dump trucks.
Once the conveyor belt was installed, load and haul costs would decrease to around R6 200/m, compared with the R13 000/m when using trucks.
PLANT PROGRESS
The company’s metallurgical consultants had started preliminary testwork on the potential for installing a high-volume optical and X-ray waste sorter ahead of the dense media separation plant.
“Such a unit could remove large volumes of internal waste from the kimberlite before processing. The K6 kimberlite contains up to 85% waste in places and the higher-grade K4 kimberlite has up to 25% internal waste,” DiamondCorp added.
Installation of a waste sorter could potentially significantly reduce water and electricity consumption in the processing plant and could also allow the kimberlite to be processed faster than the current planned 220 t/h. If the testwork was successful, a unit could be installed before the mining ramp-up from the first block cave.
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