Dual-listed base metals miner Orion Minerals will release an updated Joint Ore Reserves Committee- (Jorc-) compliant resource statement for its Prieska zinc/copper project later this month.
The Northern Cape project has a Jorc-defined maiden resource of 1.1-million tonnes of contained zinc grading 3.8% and 365 000 t of contained copper grading 1.2%.
Orion is completing a bankable feasibility study – expected to released by the second quarter of 2019 – which is investigating a simple start-up of production by mining the remnant zinc/copper mineralisation near the accessible areas of existing mine infrastructure left by former South African mining house Anglovaal.
Prieska produced 47-million tonnes of sulphide over 20 years and, according to previous mine plans, there are at least another 23-million tonnes of potential ore.
The existing mine infrastructure includes existing shafts; a regional power grid feed; bitumen access roads; and access to a bulk, treated water supply, a 1 900 m landing strip and rail infrastructure linked to the country’s ports.
Mining and environmental applications have been lodged, with mine construction work expected to start in the latter half of 2019.
Orion MD and CEO Errol Smart explains that the previous mine produced about 250 000 tonnes a month, and “we obviously want to get as close to that as possible without putting undue pressure on existing infrastructure. We believe that about 200 000 tonnes a month would be the optimal rate, which would realistically translate to a ten-year life”.
Smart says the massive sulphide zinc/copper exploration project will likely be divided into an openpit and underground operation, but stresses that 95% of the value lies in the underground resource.
Orion COO Walter Shamu says that Orion was not renovating a mine, but “building a new mine within the footprint of the old one”.
He notes that the majority of steelwork in the existing 8-m-diameter, 1-km-deep shaft is reusable and that Orion needs only to establish new hoisting mechanisms, and repair a portion of the shaft.
“The historical infrastructure gives us quick access to where the deposit is located. We have new mine layouts that are safer and more efficient and will develop those afresh. Anglovaal developed portions of the deposit, but it hadn’t finished extracting the ore; as such, the majority of the work we’re doing is for the deposit that Anglovaal left behind that we’re looking to open up.”
The new operation will be more mechanised, employing between 600 and 800 people, and Orion intends to use proven methodologies and technologies.
The first batch of advanced-stage, laboratory-scale, locked-cycle flotation tests, assessing the efficiency of the proposed mineral processing route, achieved up to 94% zinc and 86% copper recoveries into marketable concentrates.
The latest bench-scale, locked-cycle tests achieved targeted total metal recoveries ranging from between 80% and 94% for zinc and between 80% and 86% for copper into separated concentrates. The concentrates had metal grades ranging between 45% and 54% for zinc, and between 20% and 26% for copper.
Smart says the timing of the Prieska project has been ideal, as zinc and copper supplies are depleting, with prices expected to remain stable before improving on the back of increased demand.
“Zinc has been very constrained on the supply side over the past five years, as multiple large mining operations shut down and created huge shortages on the concentrate supply side.”
He notes that, while there are several large operations scheduled to come online in the near future, some of them have experienced delays.
“The Chinese refineries are clamping down in terms of environmental compliance, which means that there is reduced refining capacity. Even if mining does come on at the rate that the market is anticipating . . . there will still be a shortfall in the refined zinc market, which should drive zinc prices upward.”
While there are a lot of operations that can produce zinc in concentrate, they often have metallurgical challenges, and produce concentrate with minor element inclusions, Smart adds.
He comments that Orion’s advantage is that it can use the same processes as Prieska, but optimised through modern equipment and better, more environment-friendly reagents. “The worst case scenario is that we do as well as the previous mine, which produced a premier concentrate for decades.”