Woodlawn Zinc Copper Project Successful Metallurgical Test Work

Sydney, Australia (FSCwire) - Heron Resources Ltd. (“Heron” or the “Company”) is pleased to report the results from the metallurgical test work program focused on the underground massive sulphides at the Woodlawn Zinc-Copper Project. This work represents the first full suite of metallurgical tests undertaken on the underground mineralisation since the mine closure in 1998 and also the first tests on a combination of the tailings and zinc-copper mineralisation.

The overall results show a better than historical operational performance and reflects the advancements made in the field of sulphide flotation and in particular with fine grinding technology. These results form key input parameters for the Preliminary Economic Assessment (PEA) for the Woodlawn Underground Project. 

Woodlawn is a high-grade volcanogenic massive sulphide (VMS) deposit, located some 50km north-east of Canberra and 250km south-west of Sydney in New South Wales, Australia.

Test Work Approach

Metallurgical testing from 2005 to 2012 on the 11.6 million tonnes[1] of tailings located in the three dams at Woodlawn demonstrated that this resource could be successfully reprocessed. This involved the fine grinding and sequential flotation of copper into a copper concentrate, the lead into a lead concentrate with high silver content and the zinc into a zinc concentrate.

With recent drilling targeting the expansion of the underground resource at Woodlawn, test work on newly acquired samples of underground mineralisation began in 2014.  This test work has been carried out by Australian Mineral Metallurgical Laboratories Pty Ltd (“AMML”) in their Gosford testing facility and with input from GR Engineering Services Ltd (“GRES”). Through the application of the knowledge gained from the test work targeting the retreatment of the Woodlawn tailings and adapting this to the underground samples, good results were obtained.

Zinc-Copper Mineralisation

Table 1 presents zinc-copper (lead-silver-gold) massive sulphide mineralisation flotation concentrates generated from the test work grade/recovery curves.

The zinc-copper mineralisation is likely to represent the majority of the new mine production and the test work indicates the ability to produce these three readily saleable concentrates. Of particular note is the higher recovery of the copper to a higher grade silver bearing copper concentrate. This result has been achieved through the identification of ‘fast’ floating copper allowing the recovery circuit to accommodate for this characteristic. In addition, higher recovery of lead to a significantly higher grade lead and silver concentrate was also achieved.

Table 1: Flotation results for the Zinc-Copper Mineralisation sample (bracketed numbers represent typical recoveries achieved during previous operations at Woodlawn, c. 1992).