Blackham Resources (ASX: BLK) says “exceptional” high grades from drilling at its Wiluna mining centre have confirmed its sulphide strategy with every new hole increasing momentum and confidence.
Sulphide ore was processed through the existing circuit for 20 years between 1993 and 2013 and Blackham plans to restart that circuit to significantly increase gold production.
Altogether more than 4 million ounces of gold has been produced at Wiluna from 20 open pits and three underground mines, including the Golden Age mine which is currently a source of high grade free milling ore.
Blackham’s strategy is to increase the geological confidence in the high-grade sulphide resources around the existing mine infrastructure at Wiluna and for the company to join the ranks of Australia’s long-life major gold producers.
Results from recent drilling at the Essex and Bulletin lodes include 14.45m at 17.16 grams per tonne gold from 18.95m; 12.4m at 7.93g/t gold; 12m at 7.01g/t gold; and 6m at 53.73g/t gold, including 1m at 283g/t gold.
Grade is extremely important to the project’s economics
Executive chair Milan Jerkovic said these “outstanding” drilling results are delivering on Blackham’s stage one sulphide strategy with the company initially targeting shallow high-grade sulphides “under the headframe”.
“Our plan to convert the existing large inferred sulphide resources at Wiluna into indicated resources is gathering momentum and confidence with every new hole,” he said.
“These results will support further resource and reserves updates and mine planning work scheduled over the coming months.”
The present Wiluna underground sulphide resource averages 4.8g/t gold, the company said, but, historically, the average grade mined was between 7- 8g/t gold. The Bulletin shoot alone produced 900,000oz at an average grade of 8g/t.
Mr Jerkovic said high-grade shoot discoveries were being targeted because each 1g/t increase in the sulphide grades could result in an extra 25,000oz per annum of production in stage one and 50,000ozpa under Blackham’s stage two scenario — so grade is extremely important to the project’s economics.
A large gold system with more than 10Moz
More drilling is planned beyond June to build on the existing 10 million ounces (Moz) geological endowment at Wiluna, that figure taking into account historical production and current mineral resources.
Blackham’s combined open pit and underground resource stands at 35.5 million tonnes at 3.90g/t gold for a contained 4.45Moz, including 2.2Moz in the inferred category.
The company’s strategy is to drill out high-grade inferred mineral resources to enhance the stage one phase of the mine plan, which from September 2021 will see gold production ramp up to between 100,000ozpa and 120,000ozpa and a subsequent stage two expansion increasing to more than 200,000ozpa.
A similarly aggressive drilling program will continue in 2021 with the objective of maintaining four years of reserves in front of production.
Drilling is also ongoing at Golden Age to continue to extend free-milling cash flow.