The March quarter report for New Talisman Gold Mines Ltd (NZX & ASX: NTL) disclosed that the updated pre-feasibility study on the Talisman mine re-development at Karangahake was nearing completion.
Results of this study will be released to the market following an internal review.
NTL described the study as a “techno-economic evaluation” and was confined to evaluating the economic impact of extraction of ore from the measured and indicated resources established at Talisman.
During the quarter, NTL completed a programme of metallurgical test work designed to deliver reliable and repeatable results to inform engineering studies and cost estimates both for pilot test work for bulk sampling and for plant design in an updated PFS.
Testwork investigated the four stages of the metallurgical process namely:
- Grinding of ore to a suitable size to liberate gold.
- Recovery of free milling gold in a gravity concentrator.
- Flotation of the concentrator tails to recover additional gold.
- Final recovery of gold from concentrate.
Three samples of 25 kilograms each - representative of the Mystery Vein, Maria Vein and host rock - were sent for testing.
The ore sample from Mystery was chipped from the face of the Mystery North drive while the Maria Vein sample was retrieved from an ore stockpile. The third sample was barren andesite which is the rock in which the veins are hosted and was sent for control purposes.
Two samples, one from each vein system, were processed during the test work regime.
With results available NTL completed design of a suitable pilot plant to emulate the processes.
Managing director Matthew Hill said this plant, while small, will enable NTL to process ore won from the workings and produce gold bullion.
“The plant will consist of primary and secondary crushers, to reduce run of mine ore to mill feed size, and a mill followed by gravity concentration and flotation circuits,” he said.
“Selection and purchase of the final equipment is underway, and the company expects to complete the purchase of the equipment shortly for the commencement of pilot plant commissioning in the next quarter.”
This, he said, would put the company in the position of being able to produce gold bullion from the gravity concentrate and a high grade flotation concentrate for further refining or sale.
Given both the average grades at Mystery and the results of the metallurgical testwork a concentrate is expected to yield in excess of 46 grams/tonne (1.5 oz) on average.
At the high end of the range the potential for a 4:1 uplift would deliver a maximum of up to 160 g/t (5 oz) based on the range set out.
Hill said the equipment selected will take the concentrate through to bullion and smelting allowing NTL to sell either gold dores or, depending on the market at the time, concentrate.