Strong gold recoveries back-up De Grey’s exploration successes at Hemi
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Special Report: Not content with being one of the most successful ASX explorers this year, De Grey has now proven that strong gold recoveries are possible from its Hemi discovery.
Since making the ground-breaking Hemi discovery in mid-December 2019, the company’s drilling has continued to intersect thick, high-grade gold intervals at the Aquila and Brolgas zones.
But all the gold in the ground will be less valuable if you can’t extract, a key point that De Grey Mining (ASX:DEG) has neatly addressed with its metallurgical test work of ore from the Brolga zone.
The initial metallurgical testwork achieved 93 per cent recoveries using an industry standard carbon in leach (CIL) circuit to treat oxide mineralisation from Brolga.
Fresh rock was treated using an industry accepted circuit comprising sulphide flotation to generate a concentrate that was then oxidised using established pressure oxidation (POX) before being treated by CIL to recover 96.3 per cent of the gold.
De Grey says it will assess other methods of oxidation during the ongoing testwork.
Additional samples from Brolga and Aquila covering oxide, transitional and fresh mineralisation will also be tested to assess variability and to optimise the flowsheet.
Managing director Glenn Jardine is encouraged by the initial test work results and noted that it significantly de-risks the potential development of Hemi as a Tier 1 gold project in a Tier 1 jurisdiction.
“The testwork flowsheet used for Hemi can also be applied to De Grey’s other regional resources in the Mallina Basin,” he added.
Jardine also noted that the ongoing test work will increase the company’s understanding of the scale and metallurgical properties of the oxide, transitional and fresh sulphide mineralisation across the Hemi deposit.
De Grey’s discovery of Hemi and subsequent success in expanding its scale have been central to shares in the company rocketing over 2,000 per cent to a 52 week close of $1 on 1 July before moderating to the current price of 89.5c.
Arlington Group Asset Management said in a recent research report that the Hemi discovery “is a wonderful exploration success that can keep going as long as the drill bit keeps showing the way”.
The results to date certainly seem to fit this narrative with the most recent hits from the Aquila zonereturning a top result of 28m at 10.2 grams per tonne (g/t) gold from a depth of 117m — well above the 5g/t result that is typically considered high-grade — within a broader zone of 53m at 5.9g/t gold from 117m.
De Grey has also extended the Brolga zone with aircore drilling defining a 1,000m long by 200m wide extension to the south of the Brolga zone with assays returning results such as 16m grading 2.4g/t gold from a depth of 40m and 4m at 5g/t gold from 60m.