Horizon ponders possible Nimbus silver-zinc development

The Horizon Minerals board has decided to retain full ownership of the historic high-grade Nimbus silver-zinc project 15 kilometres east of Kalgoorlie near its flagship Boorara gold project after turning down several acquisition and farm-in proposals for the brownfields asset.

Nimbus boasts an existing high-grade resource core of 260,000 tonnes of ore at a spectacular average grade of 774 grams per tonne silver and 12.8 per cent zinc for 6.4 million ounces of contained silver and 33,000 tonnes of zinc within a larger resource.

Perth-based Horizon says it has completed a detailed review of previous geological, metallurgical and engineering feasibility study work done on Nimbus that was carried out up to 2017 when the project was put on hold due to lower commodity prices.

The company has now appointed an independent technical outfit to undertake a definitive feasibility study, or “DFS” on the possible redevelopment of Nimbus via the initial mining of the project’s high-grade mineralised lodes to produce a silver-zinc concentrate.

Horizon Minerals Managing Director, Jon Price said: “While the company’s focus remains firmly on gold, the strategic review has confirmed the potential for significant long-term shareholder value creation by retaining the asset at a time of sustained improvements in silver and zinc prices. The independent DFS team will now focus on the technical aspects and economic evaluation of mining the high-grade lodes and producing a high precious metal (silver) and zinc concentrate at site for sale to potential offtake partners.”

The Nimbus project is located within the revered greenstone belt system that extends from Norseman to Wiluna in the Eastern Goldfields province of the Archaean Yilgarn Craton.

Previous Nimbus owners, Polymetals Mining produced 3.6 million ounces of silver at Nimbus from 2003 to 2007 from the processing of 320,000 tonnes of ore that went an eye-catching 352 grams per tonne silver.

The Nimbus treatment plant was eventually decommissioned and removed and the mine site rehabilitated.

According to Horizon, Nimbus still hosts a significant global mineral resource of 12.08 million tonnes going 52 g/t silver and 0.9 per cent zinc for 20.2 million ounces of contained silver and 104,000 tonnes of contained zinc.

Importantly, the higher-grade lodes at Nimbus sit immediately below the historic Discovery open pit.

Horizon says the deposit remains open at depth and along strike and the company suggests there is significant potential to increase existing silver-zinc resources with further drilling.

Management says several expressions of interest were received to acquire or earn into Nimbus, however, the company elected to retain the project and advance a DFS across the project instead.

The scope of works for the DFS include a geological and mineralogical appraisal of the primary high-grade lodes below the historic Discovery and East pits and metallurgical test work on flotation responses and flow sheet design to produce a silver-zinc concentrate.

Horizon says the DFS will also contain a CAPEX update and take another look at operating costs for a concentrate plant that factor in potential synergies with the company’s proposed Boorara gold processing plant.

Completion of the fully funded DFS has been slated for the December quarter this year.

The 170-square-kilometre Nimbus silver-zinc project area already sits on mining leases and exploration licences. Should base metals and silver prices remain buoyant, Horizon could have another lucrative money maker on its hands that could be run in tandem with its Boorara gold production hub.

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