Metallurgy Testwork Confirms Matilda Ore as Free Milling
Perth, Oct 8, 2012 AEST (ABN Newswire) - Blackham Resources Ltd (
ASX:BLK) is pleased to report the first results of its scoping level metallurgy test work programme at the Matilda Mine as overseen by its consultants Independent Metallurgical Operations Pty Ltd. The combined gravity and leaching test work on six composite samples from a range of ore types resulted in an 87% average recovery. The average oxide recovery was 92% and sulphide/transitional average was 82% (see all tables in link below).
Previously the Matilda carbon in leach (CIL) plant processed 2.6Mt of ore at an average grade of 2.35 g/t au at 84% average recovery for gold production of 162,000oz of gold over a 6 year period. Ore processed consisted mainly of oxide material but in the order of 500,000 tonnes of fresh and transitional ore was processed through the historical CIL plant. In 1992, the final year of operation, 596,000 tonnes of ore was processed with and average recovery of 92%.
Testing was conducted on the six ore composites on a whole of ore leaching basis as well as a combined gravity / CIL basis. In all cases the gravity / CIL process delivered higher recoveries, lower reagent consumptions and faster extraction kinetics. Test work is ongoing to further optimise the process flow sheet. The leach test work did not include activated carbon which is expected to further improve recoveries.
Samples selected for composites were designed to give a fair representation of the different ore types and grades across the deposits at the Matilda Mine from recent drilling. Composite 1 was specifically selected to test a "worst-case" sulphide scenario. This sample is from outside the optimised pit areas but was included to test the recovery of gold from an extremely high sulphide intersection.
The metallurgical test work also identified a positive variation between the calculated head grade based upon the 5kg leaching analysis sample and the 50g initial assay which indicated the presence of coarse gold as confirmed by the gravity separation test work. The calculated head grade (large sample) was higher for all samples on average by 41% (range 11 to 75% higher).
Update on Development Activities
The Company has commenced mining studies of the Matilda Mine. The initial metallurgical test work and historical production and processing data provides confidence that it is technically feasible for a conventional gravity / CIL plant to be put back at the Matilda Mine to allow it to process all types of Matilda and Williamson ore plus the oxide and transitional ore from the Regent deposit.
The 2005 Williamson feasibility study concluded all rock types at the Williamson deposit are free milling. Significant test work was undertaken to confirm this. The 664,000t of oxide and transitional ore was also processed through the Wiluna Gold Plant oxide and CIL circuit during 2005/2006. The Williamson feasibility study concludes expected recoveries from a straight CIL leach in Table 3.
Metallurgical test work has also been completed on the Regent deposit. This test work also confirms the oxide and transitional ore is free milling. The expected Regent recoveries are also seen in Table 4.
The Matilda Gold Project Resource Estimate has grown to 23Mt at 1.9g/t for 1.4Moz Au on mainly shallow gold (Table 5). The free milling resources are estimated at 19.7Mt @ 1.8g/t for 1,156,000oz au or about 83% of the total resource. The refractory resource at Regent is located within 10km of the Wiluna Gold Plant refractory circuit.
As the Company shifts its focus towards development, priority will be given to improving the confidence of resources and ultimately converting resources into reserves. To this end, infill and extension drilling programs are currently in progress around the M1, M3 and M4 deposits. As part of this drilling programme more sample will be collected for further prefeasibility metallurgical and optimisation studies. Following this drilling programme the resources will be re-estimated.
Blackham management and consultants are currently focused on completing a scoping study of the various options for development of the Matilda Gold Project. The 3 main mining centres within the project are all within 10km by existing haul roads of the old Matilda plant footprint and its infrastructure and 26kms by existing haul roads of the Wiluna Gold Plant. The Scoping study is expected to be finalised by the end of October.
The Company is delighted with the rapid progress of the Matilda Gold Project. In less than 12 months the resources have grown over 350%. The Company's focus is now on the development of the Matilda Gold Project whilst continuing to explore the high grade underground potential that is yet to be systematically investigated.
For all included table data, please visit:
http://media.abnnewswire.net/media/en/docs/ASX-BLK-607132.pdf
About Wiluna Mining Corporation Ltd
Wiluna Mining Corporation (ASX:WMC) (OTCMKTS:WMXCF) is a Perth based, ASX listed gold mining company that controls over 1,600 square kilometres of the Yilgarn Craton in the Northern Goldfields of WA. The Yilgarn Craton has a historic and current gold endowment of over 380 million ounces, making it one of most prolific gold regions in the world. The Company owns 100% of the Wiluna Gold Operation which has a defined resource of 8.04M oz at 1.67 g/t au. In May 2019, a new highly skilled management team took control of the Company with a clear plan to leverage the Wiluna Gold Operation's multi-million-ounce potential.
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