Since acquiring the Century Mine, the Company restarted operations through the reprocessing of the large tailings Ore Reserve on the mine site.

The current tailings Ore Reserve provides base production, with in-situ resources providing additional production. The two in-situ deposits on the mining lease (Silver King and East Fault Block) are located less than 2km from the processing plant and have been used as the feed source for the plant, with two additional deposits on the Company’s leases (South Block and Watson’s Lode) to be assessed for potential mine life extension in due course.

Century Tailings Deposit
A single substantial tailings deposit exists at Century, generated from 16 years of large scale operations from the Century open pit.

Substantial recoverable zinc mineralisation exists in the tailings at Century, due to the historical focus on throughput maximisation as opposed to recovery maximisation. The nature of the original Century ore required extended flotation time and given the scale of the original Century deposit (105Mt at 12% Zn) a high throughput processing plant was constructed, achieving relatively modest recoveries (74% in 2015) over the life of operations.

Three independent metallurgical studies have been completed on the Century Tailings Deposit, demonstrating the tailings may be reprocessed through the existing plant on site with minor modifications to achieve recovery of >60% of remaining zinc minera ........

Hydraulic mining of the Century tailings deposit is undertaken via top-down hydraulic mining method. Up to four active water cannons are located on top of the mining bench and use high pressure water to fluidise the tailings. The resultant slurry gravity feeds to a sump, in which multiple submersible pumps transfer the tailing to screen after which it is pumped to the Century concentrator. The mine plan has broken the deposit into 3 horizontal passes, with the hydraulic cannons working in strips and blocks with typical strip widths of 15-20 meters. The floor of the tailings facility will be cleaned up, utilising a combination of hydraulic mining, dozers and excavators. The current mining activities show the appropriateness of the method as the basis of the Ore Reserve.

During the hydraulic mining process, a 300mm material layer will be left on the floor of the deposit, which is accounted as ore loss. Additionally, a dilution of 100mm at the bottom of the deposit for non-tailings material is applied to the resource model. This final layer including the 300mm of ore loss and 100mm of dilution will be removed in the final clean-up pass. A mining recovery of 95.5% has been assumed for all mining blocks removed with the hydraulic cannons which is based on the mine call factor estimated from monthly reconciliation data.

The Optimisation Study referred to in this announcement is an update to the original In-situ Feasibility Study of the potential of combining t ........

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