2 Apr 2015 07:00
Berkeley Mineral Resources PLC
("BMR" or the "Company")
Leach processing selected for pilot plant
Background
The Company announced on 11 December 2014 that the Directors were undertaking a peer review of the definitive feasibility study ("DFS") for processing the washplant tailings ("WPT") at Kabwe.
The Company subsequently announced on 2 February 2015 that related test work on the WPT was well advanced.
It also announced on 2 February 2015 that preliminary metallurgical and mineralogical test work would start later that month on the leach plant residue tailings at Kabwe ("LPR"), the Company's largest JORC compliant resource.
Dr Geoff Casson, the General Manager of the Company's Zambian operations, was in attendance throughout the test work referred to above. He presented his findings in Zambia last week to Jeremy Hawke, a Director of the Company, who then reported his conclusions to the Board.
In light of these findings, the Board resolved yesterday to select a leach processing methodology for the pilot plant processing of the WPT and LPR.
Multi-spiral gravity separation of the WPT
The Directors arranged for a 5 tonne sample of WPT to be subjected to a full multi-spiral, gravity separation pilot test by spiral process specialists in South Africa to establish the potential recovery and grade of zinc and lead under simulated plant operating conditions.
Notwithstanding the Board's initial preference for multi-spiral gravity separation, the results of this test work ultimately did not replicate either the potential recoveries or grades of the zinc and lead in the final product claimed in the DFS, and metal recoveries were materially inferior to those reported in the DFS. In summary, the volume of fine material generated after scrubbing exceeded 50% of the ore feed, which proved untreatable by multi-spiral gravity separation.
The alternative multi-gravity separation technology proposed in the DFS, which is often better suited to fine material, was also considered. The Directors, after carefully examining previous test work results and taking into account the high proportion of finer feed, rejected this technology as impractical and more costly, without offering a commensurate improvement in zinc and lead recoveries.
A further attempt to improve zinc and lead recoveries by pre-treating the spiral feed was undertaken using Wet High Intensity Magnetic Separation. The objective was to reduce the high percentage of iron (ferrite) competing with the zinc. Whilst some iron was removed, the losses of zinc and lead, locked within the iron minerals, was unacceptable and led to low recoveries of both.
The Directors therefore concluded that the DFS, which had been commissioned in August 2013 and the results of which were accepted without sufficient challenge by the former Board chaired by Masoud Alikhani, does not provide an acceptable basis for selecting an appropriate processing methodology for the Kabwe tailings.
Furthermore, the Directors resolved yesterday not to pursue gravity separation as a potential methodology for metal recovery and the DFS has been removed from the Company's website.
Leach processing of tailings
The metallurgical and mineralogical test work on the LPR using leach processing, which was resurrected by the new Board earlier this year, has now advanced to mini-pilot stage.
The Board is pleased to report that this proprietary process, which is being developed by the Company working with technical partners, provides a credible alternative for the recovery of zinc and lead from both the WPT and LPR tailings. Results to date are encouraging, in that the zinc and lead recoveries achieved are approximately 55% and 85%, respectively, each of which represents an improvement on the previously claimed recoveries from gravity processing in the DFS. Furthermore the process generates no toxic effluents.
The Directors therefore yesterday selected leach processing as the methodology for processing both the WPT and LPR tailings, and expect to finalise the design parameters for a pilot plant in the next few weeks.
Although the pilot plant is yet to be costed and ordered, the Board is confident that BMR has sufficient resources to initiate pilot processing without recourse to BMR's shareholders.
Finally, the Directors have held preliminary discussions with the Director General of the Zambia Environmental Management Agency ("ZEMA") to explore how best to seek permission for the establishment later this year of a leach processing pilot operation for both the WPT and LPR tailings at Kabwe. After an explanation of the potential change in process, ZEMA recommended that the Company submit a brief project description without delay and advised that sympathetic consideration would be given, with advice on the most expedient route to be taken, to gain ZEMA approval.
Note:
This release has been reviewed by Geoff Casson, B.Sc. (Hons), PhD, R Eng (Zambia), Member Engineering Institute of Zambia (Metallurgy), General Manager of the Company's Zambian subsidiary, Enviro Processing Ltd, who is a Qualified Person in accordance with the guidance note for Mining, Oil & Gas Companies issued by the London Stock Exchange in respect of AIM Companies.
Commenting on the above, Alex Borrelli, Chairman of BMR, stated:
"I am pleased to report, notwithstanding the flaws in the DFS, demonstrable progress on the potential recovery of zinc and lead concentrates from the tailings using a leach processing methodology. We now have the opportunity to realise significant value from the washplant and leach plant deposits, commencing with the establishment of a pilot plant scheduled for later this year. We look forward to keeping shareholders informed of our progress."
For further information:
Berkeley Mineral Resources Plc 07747 020 600
Alex Borrelli, Chairman
WH Ireland Limited 020 7220 1666
Chris Fielding, Head of Corporate Finance