Test work has given New Talisman Gold Mines Ltd (NZX & ASX: NTL) some options on how to treat high grade gold-silver ore from the historic Talisman mine at Karangahake.
The company produced an update yesterday following more exploration and test work on ore from the three main veins – Maria, Mystery and Crown-Welcome.
The Maria Vein is seen as the major contributor and contains about 91% of the mineral resource of 469,000 ounces gold equivalent, within the Dubbo, Bonanza and Woodstock zones.
NTL said the average grade in these zones was estimated at 22. Grams/tonne, 23.6 g/t and 6.3 g/t Au (eq) respectively,
Some of the high grade hits have been in hole BM 37 which yielded 1.8 metres at 656 g/t gold and 2,080 g/t silver.
Metallurgical test work was designed to deliver reliable and repeatable results which will be used for engineering studies and cost estimates both for pilot test work during bulk sampling and to inform design in an updated pre-feasibility study.
The company said an important output from test work was to determine the optimal grind size to liberate gold contained in the ore. Two grind sizes were tested with the milled product pulped to 50% solids and the resultant pulp was subjected to gravity concentration via a Knelson centrifugal concentrator.
The primary concentrate was upgraded through hand panning to provide a final concentrate mass yield approaching that of operating Knelson installations.
Final free gold concentrate (pan concentrate) was assayed via total fusion to eliminate sampling error and nugget effect. Secondary concentrate and final tailings were dried, weighed and split for gold assay.
“Results from this show that 61.3% of gold in Dubbo ore, and 81.9% of gold in Mystery ore can be recovered directly through this process.
NTL said following pilot testing, the company will be able to use only environmentally benign reagents for gold recovery which supports the goal for the Talisman mine to be a responsible, environmentally sustainable operation.
Chief operating officer and principal mining engineer Wayne Chowles said “The results of this test work provides the necessary hard data with which to proceed with forward planning and takes us an important step closer to realising the potential of this magnificent orebody”
Chief Executive Matthew Hill said the test work will help with pilot plant design.
It is expected that the plant will be modular and scalable allowing components to be added as production volumes increase.
“Completion of this test work demonstrates the successful ability to extract high grade concentrate from the existing orebodies without the use of any hazardous chemicals,” Hill said.
“From a processing perspective this is about as clean and environmentally friendly for treatment of gold ore as it gets with natural rock being re-used as backfill.
“This is a key milestone for the company and allows us to develop a saleable product without the need for external parties.”