Additional Positive Metallurgical Test Results
Improved Lithium Recoveries at the Ewoyaa Lithium Project
Ghana, West Africa
IronRidge Resources Limited (AIM: IRR, “IronRidge” or the “Company”), the African focussed minerals exploration company, is pleased to report additional very positive metallurgical test results from the Ewoyaa Lithium Project within the Cape Coast Lithium Portfolio in Ghana, West Africa.
Figures and Tables referred to in this release can be viewed in the PDF version available via this link:
Ø Additional test work completed to improve lithium recoveries in coarse grained type P1 and finer grained type P2 pegmatites.
Ø Larger scale gravity processing of P1 mineralisation inclusive of middlings fraction confirms up to 74% recovery of over 6% spodumene concentrates.
Ø Mass yields, of up to 22%, are considered to be high by peer comparison and support an economic case for a lower throughput and lower capital intensity starter project.
Ø Gravity processing of P2 mineralisation inclusive of middlings fraction delivers 51% recovery of 5.5% spodumene concentrates for blending.
Ø Further project enhancements available by processing of fines generated by crushing.
Ø Opportunity to recover feldspar by-products for the local and European ceramics industry identified.
Commenting on the Company’s latest progress, Noel O’Brien, metallurgical consultant to IronRidge, said:
“We are very pleased to have refined recoveries and mass yields, which we believe are high by peer comparison, without loss of concentrate grade achieved through further larger scale test work at Ewoyaa. All of this was achieved whilst maintaining a simple gravity only process flow sheet design philosophy.
“The Ewoyaa Project can be further enhanced by later stage flotation to capture lithium losses in fines generated during crushing, albeit this represents a relatively small volume of the lithium credits in the project.
“Additionally, test work has defined a potential valuable by-product stream in high quality feldspar concentrate with low contaminants, which could be suitable for the local and European ceramics industry.”
Commenting on the latest test-work results, Vincent Mascolo, CEO and MD of IronRidge Resources, said:
“We are very pleased with the recovery improvements achieved through re-crushing of middlings whilst maintaining concentrate grade.
“We will continue to explore all avenues available to us for any project enhancements to maximise value for all shareholders.
“The recognition of further lithium recoveries from fines generated by crushing, as well as the favourable composition of our feldspar tailings waste stream for potential sale into the ceramics industry, represent valuable project enhancements.”
New Metallurgical Test Work
The first phase of metallurgical testing on drill core from the Ewoyaa lithium deposit (JORC 2012 compliant 14.5Mt at 1.31% Li2O in the Inferred and Indicated category) was reported in RNS’ of 21 May 2019 , 25 June 2019 and 28 January 2020.
The initial results from testing the core samples demonstrated good metallurgical response for both the course P1 type pegmatites and the finer grained P2 type pegmatites. These results were based on laboratory bench scale Heavy Liquid Separation (‘HLS’) variability testing and indicated idealised recoveries of 6% Li2O concentrates ranging from:
· 62% to 78% for P1 mineralisation at mass yields of 12-22% and
· 30-50% for P2 mineralisation at mass yields of 5-10%.
Additionally, X-Ray Diffraction (“XRD”) mineralogical data demonstrated that spodumene was the dominant lithium bearing mineral in all concentrates produced. Resource evaluation to date has demonstrated that P1 type pegmatites are dominant in the Ewoyaa deposit, with a ratio of P1 to P2 of around 60% : 40%. Within each type there are zones of transitional and fresh mineralisation which are expected to behave slightly differently in a processing plant. Of the total resource, 12% is weathered transitional and 88% is primary fresh material.
These initial results were encouraging in terms of being able to present a business case based on low cost gravity separation technology to generate commercial grade concentrates in economic quantities.
Further work has been done on the first stage of improvement, with P1 mineralisation being tested at a larger scale using a 100mm Dense Media Separation (‘DMS’) cyclone as well as testing the effect of re-crushing middlings, and also the effect of re-crushing middlings on the recovery from P2 mineralisation still using HLS.
P1 Fresh Mineralisation:
A 54kg composite of fresh P1 mineralisation grading 1.68% Li2O, was crushed to 6.3mm and screened at 0.5mm. The first pass DMS results at 2.9 SG produced 67% recovery at an elevated grade of 6.29%. When normalised to 6% grade, this corresponds to a recovery of 69% at a mass yield of around 21%.
Re-crushing of the intermediate grade gravity middlings fractions has been shown on a number of projects to liberate more spodumene and result in increased recoveries. The middlings fractions from this test were re-crushed at 3.35mm and put through the DMS again and the combined result showed a recovery of 75% recovery at a grade of 5.88%. When normalised to 6% grade, this corresponds to an increase in recovery to around 74% at a mass yield of 22%, (refer Table 1 ).
Overall, the results for P1 fresh mineralisation demonstrate that a gravity recovery of 74% can be achieved and that re-crushing the middlings will assist in maintaining this recovery.
P1 Transitional Weathered Mineralisation:
A 24kg composite of P1 transitional mineralisation was processed in the 100mm cyclone following the same procedure described above for the fresh mineralisation. The grade of the composite was 1.37% Li2O.
The first pass results without re-crushing showed a recovery of 60% at an elevated grade of 6.27% and a mass yield of 13%. When normalised to 6% concentrates, this corresponded to a recovery of 63% at a mass yield of 15%. After re-crushing the middlings, the results also showed an improvement to 70% recovery, at a grade of 6.0% and a mass yield of 16% (refer Table 1 ).
These results demonstrated that 70% recoveries could be obtained from transitional material, again with the assistance of re-crushing the middlings.
P2 mineralisation is finer grained than P1 and generally lower grade. It makes up around 40% of the deposit which represents a significant part of the overall lithium inventory and will in all likelihood be processed by itself or as a blend from time to time.
To date, only preliminary smaller scale HLS tests have been done on P2 mineralisation to gauge the response of it to gravity processing. The results below show the P2 ores benefit from re-crushing the middlings with the recovery of fresh ore increasing from 42% to 46% at a grade of 5.5% and the recovery of transitional ore increasing from 55% to 61%at a grade of 5.6% (refer Table 2 ). There was insufficient data to normalise the P2 recoveries to 6% concentrate, but extrapolation of the data suggests an overall recovery of about 51%.
Around 15-20% of the contained lithium is in the -0.5mm fines fraction generated by crushing that is screened out before gravity processing, as gravity processing below this size is challenging. A number of mines utilise flotation to recover value from this fraction and a preliminary series of tests were done on P2 Fresh -0.5mm mineralisation, with a grade of 1.02% Li2O, to gauge the amenability of Ewoyaa spodumene to standard flotation techniques.
The results were encouraging with 6% concentrates being produced at a flotation recovery of 57% (49% overall after allowing for desliming and magnetic losses) and a mass yield of 11.1%. This demonstrated the potential to improve overall recovery by capturing lithium loss due to fines generation during crushing, and so expand the economic lithium inventory of the deposit.
The recent work highlighted that the lighter gravity fractions of Ewoyaa mineralisation; the SG2.6 floats, have elevated levels of potassium (‘K2O’) and sodium (‘Na2O’) minerals. In just about all cases from the test work completed, the total of K2O + Na2O is greater than 10%. This level is considered to be commercial grade feldspar and the ceramics industry has a significant requirement for such material.
Based on this preliminary analysis, it is estimated that upwards of 20% of the plant feed material could be recovered as a saleable feldspar product. For a plant designed to process one million tonnes per year, this translates to around 200,000 tonnes or more of this product per year.
This product could be suitable for the regional ceramics industry and the wider international industry.
Competent Person Statement
Information in this report relating to the exploration results is based on data reviewed by Mr Lennard Kolff (MEcon. Geol., BSc. Hons ARSM), Chief Geologist of the Company. Mr Kolff is a Member of the Australian Institute of Geoscientists who has in excess of 20 years’ experience in mineral exploration and is a Qualified Person under the AIM Rules. Mr Kolff consents to the inclusion of the information in the form and context in which it appears.
The information in this announcement that relates to metallurgical results is based on information compiled by Mr Noel O’Brien, Director of Trinol Pty. Limited. Mr O’Brien is a Fellow of the Australasian Institute of Mining and Metallurgy (AusIMM) and has sufficient experience which is relevant to the style of mineralisation and type of deposit under consideration and to the activity which he is undertaking to qualify as a Competent Person as defined in the December 2012 edition of the “Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves” (JORC Code). Mr O’Brien consents to the inclusion in the report of the matters based upon the information in the form and context in which it appears.
Certain information contained in this announcement would have been deemed inside information for the purposes of Article 7 of Regulation (EU) No 596/2014 until the release of this announcement.
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