Gold mining company African Gold Group in July announced the final metallurgical test results from its comprehensive sulphide testwork programme, which incorporated variability testing to determine the optimal process route of the ore across the extent of the orebody at its Kobada mine in Mali.

The company is continuing its work on updating mineral resource estimates and an updated definitive feasibility study (DFS) to incorporate additional drilling and the sulphide testwork results.

The comprehensive metallurgical testing programme was conducted by specialised minerals processing technology provider Maelgwyn South Africa on composite samples from all defined mineral zones (north, south, and central domains) of the main shear zone.

The final stage of this process, the variability testing, has proven the consistency of being able to treat the sulphides across the extent of the orebody.

Highlights from the metallurgical testing showed that gravity gold recovery values vary from 40.40% to 73.18% with an eighty-fifth percentile of 61.52%.

These results indicate that the sulphide ore at Kobada is amenable to gravity recovery.

Additionally, overall gold dissolution at 93.87% confirms initial findings that consistent overall gold dissolution of above 90% can be achieved on the sulphide ore.

The results indicated that cyanide consumption values vary from 0.14 kg/t to 0.46 kg/t with an eighty-fifth percentile of 0.34 kg/t, indicating low cyanide consumption of the sulphide ore.

Additionally, lime consumption values vary from 0.23 kg/t to 0.31 kg/t with an eighty-fifth percentile of 0.30 kg/t, confirming low lime consumption of the sulphide ore.

“The finalisation of our comprehensive sulphide metallurgical testwork programme, culminating in the variability testwork, shows us that sulphides at the Kobada gold project can be treated through a gravity and carbon-in-leach (CIL) process,” said African Gold Group CEO Danny Callow.

He added that the process design on gravity and CIL for the oxides, as presented in its July 2020 DFS, is suitable for treating the sulphides as well, and this will allow the company to add substantial resources to its overall resource base.

“The sulphides are free-milling, show excellent recoveries and consume low amounts of lime and cyanide, making this a very efficient operating cost process.

“The results will feed into African Gold Group’s updated DFS, allowing it to incorporate sulphides into the life-of-mine plan and will add additional reserve ounces to its economic models.”

Callow adds that the wider testwork programme has been highly successful and confirms Kobada’s excellent potential as a future new mine in Mali.

“We are looking forward to delivering an updated study in the third quarter of 2021.”

Testwork Results

Upon completion of recovery optimisation testwork on a composite sample, the optimum conditions selected were tested on variability samples to determine if the selected process route and optimum conditions selected are applicable across the entire orebody.

Six variability samples were selected from the North, South and Central zones.

The selected process route on the oxide ore was gravity followed by cyanidation.

Initial scouting testwork on the sulphide ore using the same process route as for the oxides showed gold recovery above 90% with low cyanide and lime consumption.

Therefore, the selected recovery process for the sulphides was gravity followed by intensive cyanidation on the gravity concentrate and cyanidation on the gravity middlings and tails.

Callow concludes that the company is well under way to deliver an updated DFS in the third quarter of 2021.