De Grey’s Hemi gold discovery is already one of the most exciting in recent times and now pilot-scale test work has indicated that recoveries are equally impressive.

The first in a series of pilot-scale tests has achieved overall recovery of 91.9% on a 4.5t sample of lower grade (0.9g/t) mineralisation from the Brolga deposit.

Notably, the recoveries correlate well with previous test results showing gold recovery increasing alongside corresponding increases in the head grade – 93% recovery from ore grading 1.4g/t gold and 97.5% in bench scale sample grading 2.6g/t gold.

De Grey Mining (ASX:DEG) noted that testing was carried out first on Brolga as it is likely to provide first production from Hemi.

However, there is good reason to believe that pilot-scale testing of the other deposits will have similar results as bench-scale testing to date has returned similar recovery outcomes.

“These new pilot testwork results on the 4.5 tonne bulk sample taken from the Brolga deposit continue to demonstrate high metallurgical recoveries across the deposits at Hemi,” managing director Glenn Jardine said.

“The metallurgical recovery at 91.9% on a feed grade of 0.9g/t Au is outstanding.

“Our ongoing metallurgical testwork program continues to provide confidence in the process flowsheet to achieve high gold recoveries from Hemi and the regional deposits across the Mallina gold project.”

Positive Brolga results drive further testing

The Brolga sample was collected from five diamond holes and the ore was crushed and homogenised prior to continuous pilot scale milling, classification and sulphide flotation, producing concentrate that was sent for pressure oxidation before the oxidised residue was subjected to cyanide leaching.

Products generated from this pilot are being used for downstream testwork as part of ongoing metallurgical and process engineering studies including a further Albion process test program.

The metallurgical testwork results will feed into the Pre-Feasibility Study (PFS) for Hemi which is due to be released in the September quarter this year. De Grey has said it is hoping to improve on key outcomes from last year’s Scoping Study in the PFS numbers.

Further pilot-scale testing will be carried out on individual deposit and composite deposit samples and at various grades from Hemi on a combination of material from the Brolga, Diucon, Eagle and Falcon deposits.

De Grey also plans continued variability bench-scale work across all Hemi deposits with a focus on Diucon and Eagle as well as the weathered ore domains.




This article was developed in collaboration with De Grey Mining, a Stockhead advertiser at the time of publishing.


This article does not constitute financial product advice. You should consider obtaining independent advice before making any financial decisions.