ASX-listed Newfield Resources says underground development drill and blast operations continue at its Tongo diamond mine in Sierra Leone, and to date the decline development has advanced some 76 m. The ongoing development of the 6 m x 4 m decline tunnel is critical to the project progress, as each blast brings development closer to the first ore stopes. The selected mining method is traditional shrinkage stoping (with an 85 cm mining stope width). This method has been commonly used in similar kimberlite dyke mining operations in South Africa. Forecast diluted, recovered diamond grades average 1.0 ct/t across the initial eight-year Reserves-only life-of-mine.
The decline has initial dimensions of 6 m by 4 m for the first 200 m and is located approximately mid-way between the high grade Kundu and Lando kimberlite dykes. After 200 m the decline will be split into two smaller declines of 4 m x 4 m each which will respectively be developed towards the Kundu kimberlite to the north and the Lando kimberlite to the south in accordance with the detailed mine design. The underground mining machinery currently comprises two drill jumbos, two 15 t haul trucks and two LHDs all supplied from an OEM in China but being leased through an agreement with Australia’s BauMart.
On the COVID-19 crisis impact, the company states: “Whilst supply chain delivery of spares and consumable items has been severely impacted by interim limitations imposed by local and international institutions, the company presaged these restrictions and made special arrangements before the limitations were implemented, such that it is possible to continue underground development operations, at least for the short term. The development work at Tongo therefore continues within the constraints of the new COVID-19 safe working protocols. Progress has been achieved with 133 LTI free days as at the 31st March 2020.”
Mine infrastructure construction has continued with good progress made on the 100 t/h plant earthworks foundations and civils. Furthermore, construction has continued on mine administrative offices, the site clinic and establishment of a potable water supply at the main camp and mine site. At the mine site, the change house, lamp room and offices are approaching completion. “Supply chain delivery of construction and mining materials is now experiencing tightening and is likely to delay completion of some of these structures. The likely impact of such delays on the overall project programme is bei ng actively monitored as events unfold in Sierra Leone with the COVID -19 virus pandemic.”
METC Engineering of Johannesburg reports that construction of the 100 t/h plant components has been suspended due to a strict lockdown in South Africa. This will undoubtedly affect delivery of the processing plant, due to commence in Q2 of 2020, which will have a knock-on effect on the availability of the 100 t/h plant once ore is available for processing. “However, the company has a back-up plan in place, which involves utilising the existing bulk sample plant to process the first ore that arrives from the underground stopes. This plant has sufficient capacity to process the first ore deliveries as stopes are gradually added to the production capacity. This back-up plan will mitigate the effects of the likely delay in the delivery of the 100 t/h plant noted above and will support the overall project objective of achieving first diamond production by year’s end.”