Ongoing Metallurgical Testwork To Examine Variety Of Oxidation Processes
De Grey Mining Limited (ASX: DEG) has received positive results from a metallurgical testwork programme at its Hemi and regional deposits, located approximately 60km south of Port Hedland in Western Australia.
The company is undertaking a comprehensive metallurgical testwork program across each of the mineralised zones at Hemi (Brolga, Aquila, Crow and Falcon) and the regional deposits of Mallina and Withnell. The other main regional deposits of Toweranna and Wingina are free milling and will be able to be treated through a conventional CIL circuit.
Recovery of free gold through a gravity process using a Knelson gravity concentrator was tested on three composite samples of Brolga mineralisation. The samples returned gravity recovery results of 12.4%, 27.3% and 12.1%.
Managing Director, Glenn Jardine, said these recoveries may not be representative of all mineralised zones at Hemi and gravity testwork will continue on composite samples from Brolga, Aquila, Crow and Falcon. However, the potential to achieve a meaningful level (e.g. 10%) of gravity gold recovery without the need for either CIL or flotation/oxidation processes is positive.
“The results from our ongoing metallurgical testwork programme continue to give us confidence in the multiple pathways we have to achieve high gold recoveries from Hemi and the regional deposits at Mallina,” Mr Jardine said.
“Each of the potential oxidation processes delivered high recoveries, with POX and Albion® the standouts respectively at 97% and 98%.
“Further testwork and trade off studies underway will enable us to optimise the various aspects of our metallurgical program in terms of capital, operating costs, recoveries and operability.”
Meanwhile, a high level, initial trade-off study considering three potential oxidation processes has been conducted by GR Engineering Services. The study considered the capital and operating costs, commissioning, operational simplicity and metallurgical recoveries of the three oxidation process options.
POX and BIOX are well known technologies used at gold projects throughout the world. The Albion process has also been identified as having potential application at Hemi with benefits including:
• Capital and operating costs
• Flexibility to cope with changes in ore type and sulphide content • Circuit and operational simplicity
• Straightforward start-up and shutdown
• Atmospheric leaching
• Low pressure oxygen plant
The Albion process is currently in use at large base metals refineries in Spain and Germany and at a sulphide gold mine and plant in Armenia.
However, metallurgical testwork and studies remain at an early stage and POX, Albion and BIOX oxidation processes all remain under active consideration for use at Hemi.
As noted, further oxidation testwork will be conducted on each of the zones at Hemi before one or more preferred oxidation process routes are selected to be carried forward into optimisation metallurgical testwork and engineering studies.
