Xtract Resources Plc (AIM: XTR) has announced the start of initial production at the Silverking copper-silver project in Zambia.
The project is operated through a joint venture with Oval Mining Ltd, which holds the Small-Scale Mining Licence covering Silverking in Zambia’s Mumbwa District, and Cooperlemon Consultancy Ltd.
Oval has commenced processing mixed oxide-sulphide ore through the joint venture’s flotation plant, following recent upgrades designed to support increased processing capacity.
The operator is targeting an optimised throughput rate of 28 tonnes per hour.
Xtract said sufficient sulphide mineralisation is present within the near-surface section of the orebody to support direct flotation. The oxide component has also demonstrated that it can be treated through the addition of reagents, allowing the mixed run-of-mine feed to be processed through the flotation circuit.
Further reagent trials are underway to stabilise concentrate grades, which are currently fluctuating between 20% and 35% copper. The target optimised concentrate grade is approximately 28% copper.
Run-of-mine grades from the upper section of the orebody are currently between 0.80% and 1.1% copper and between 11 and 68 grams per tonne silver.
Executive chairman Colin Bird said the start of operations and initial concentrate production represented an important milestone for Silverking.
“Production is now being progressively ramped up and, while concentrate grades remain variable as the balance between oxide and sulphide material evolves, the plant’s demonstrated ability to recover oxides is encouraging,” he said.
Bird added that reagent optimisation work is continuing to improve copper recovery and that the team is completing its fifth blast in the open pit, bringing operations closer to predominantly sulphide ore and potentially more stable operating conditions.
Drilling has defined a high-grade, bornite-rich vertical plug from a depth of 60 metres to at least 140 metres. This is surrounded by a 200-metre by 110-metre chalcopyrite-rich envelope projected to approximately 170 metres depth.
Two substantial chalcocite-bornite vein systems have also been identified cutting across the main mineralised body, with potentially mineable widths.
Oxide and sulphide mineralisation extends from surface to around 60 metres over the centre of the deposit and to 135 metres northwest of the core mineralised zone.
The mineralisation remains open at depth. Previous drilling returned an intersection of 4 metres grading 7.67% copper and 63.5 grams per tonne silver from 228 metres downhole in hole SKIDD018.
Xtract plans further drilling to test the system to approximately 350 metres vertical depth.
The company is also evaluating the development of a decline to access the high-grade core at depth, with final mine planning expected to be informed by upcoming drilling results.
Deposit modelling has incorporated 895 diamond drill core samples, 131 partial trench assays and 281 partial blast-hole assays.
Of the samples analysed, 19 returned copper values above the initial laboratory detection limit of 10%. Seven of these were subsequently submitted for high-grade analysis, returning copper values of up to 41.96%.
Xtract stressed that Silverking remains at an early stage of production and is still undergoing commissioning and optimisation.
The company said there can currently be no assurance over steady-state throughput, concentrate tonnage or final concentrate grade until further optimisation and reagent trials have been completed.