De Grey Mining Limited - Hemi Process Flowsheet Selections

De Grey Mining Limited ASX Announcement 2 De Grey Mining Limited (ASX: DEG, 'De Grey' or the 'Company') is pleased to report the results of two important process flowsheet selections, the outcome of a comprehensive 9 month trade-off study completed by the PFS process engineer - Wood Australia.

Each represent key inputs into the well advanced PFS for the Mallina Gold Project due in the September Quarter 2022.

Flowsheet Summary Description

Ore will be crushed and ground in the comminution circuit before being fed to the flotation circuit. Any gravity recoverable gold will be recovered prior to flotation with the use of, for example, a Knelson or Falcon concentrator. Testwork has shown gravity recoverable gold is present in the Hemi and regional mineralisation. The extent of gravity recoverable gold will continue to be assessed through testwork

The flotation circuit will process gold bearing sulphides in Hemi ore producing a 'low mass pull' gold rich sulphide concentrate. The POx circuit is designed to receive the gold rich sulphide concentrate from the flotation circuit. The Pox circuit will have a throughput of 8% (0.8Mtpa) of the throughput of the comminution circuit. The POx circuit will convert the sulphide concentrate to a gold bearing residue amenable to standard carbon in leach (CIL) processing. The underflow from flotation is also amenable to standard CIL processing. Both streams will enter the CIL circuit followed by electrowinning to produce gold bars on site. This has numerous benefits for the POx circuit including lower capital and operating costs compared with projects that require whole of ore treatment through POx. Tailings from the CIL circuit will be pumped to a tailing storage facility.

De Grey Managing Director, Glenn Jardine, commented: 'The use of a HPGR in the comminution circuit and POx for the oxidation circuit represent the best technical, environmental and economic outcomes for a proposed plant of this scale. HPGR and POx are robust, well proven and accepted technologies that have been chosen after extensive testwork. Pressure oxidation demonstrated lower reagent usage and carbon intensity, lowest greenhouse gas emissions and the highest gold recovery of the processing options considered for Hemi mineralisation. We will carry the selected process flowsheet through the Pre-Feasibility Study currently underway and due for completion in the September Quarter, 2022. The significant increase in the scale and confidence level of Mineral Resources along with the robust flowsheet selected for processing at Hemi enhance and de-risk the project.'

Contact:

Glenn Jardine

Tel: [phone]

Email: [e-mail]

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