- Preliminary metallurgical recovery test results of 83.4% to 97.5% significantly exceed historical assumptions for lead, zinc, silver and gold recoveries.
- Argent is aggressively pursuing Kempfield economic viability through several programmes currently directed at the following goals:
o Increasing the Mineral Resource through infill drilling of the JORC compliant Exploration Target estimated by resource specialists H&S Consultants Pty Ltd;
o Optimising processing plant feed grades in financial modelling scenarios; and
o Optimising metal recoveries through further identified metallurgical testwork.
- Project economic potential further boosted by LME zinc prices at 10 year highs.
PRELIMINARY METALLURGICAL TEST RESULTS EXCEED HISTORICAL ASSUMPTIONS
About the metallurgical test results
Argent's metallurgical testwork has yielded excellent recoveries for Kempfield silver, gold, zinc and lead in a standalone flotation processing environment. The recoveries to an initial bulk metal concentrate are substantially higher than historical feasibility study assumptions for Kempfield deposit material, as summarised in the following table (see link below).
About the purpose of the metallurgical tests
Argent's goal for the testwork is to establish the potential for higher metallurgical recoveries to separate lead and zinc concentrates in a standalone flotation processing environment than the existing assumptions based on historical testing. The historical testing had primarily focused on carbon-in-leach (CIL) recoveries for silver and gold from oxide and transitional material.
Whereas the historical flotation tests were performed on residue from the preceding CIL tests (which can introduce complexities for subsequent flotation recoveries), the recent tests were performed directly on drill core samples from primary material.
The metallurgical testwork will be used to devise the most effective processing flowsheet for optimal recovery of metals from Kempfield-specific material into two separate concentrates of saleable grades as the Company continues to advance the Kempfield project toward the ultimate goal of production.
About the metallurgical testwork
Under the supervision of metallurgical engineer Mr. Roland Nice, Kempfield material was selected from two diamond holes drilled in 2016 (AKDD183 and 187) and shipped to Australian Minmet Metallurgical Laboratories Pty Ltd (AMML) in Gosford NSW, who is conducting the testwork.
The drill core samples were crushed to 3.25 mm and divided into two equal halves. One half was retained, while the other was combined to form an 18 kg composite. The composite was further divided into 18 portions, each 1 kg for individual testwork. All samples were frozen in order to enhance the life of the samples.
The metallurgical engineer devised a series of tests, commencing with three bench-scale flotation procedures.
About the preliminary results
The first three tests (AF1, 2 and 3) showed that the sulphides float quite readily. One test incorporated a bulk flotation test AF3 with the preliminary recovery results summarised in Table A (see link below). The zinc and lead recoveries, in particular, significantly exceed the historical feasibility study assumptions of 55% (see Table A in link below).
Test AF3 comprised a primary grind of P80 = 53 Micronsm, followed by a bulk sulphide flotation for 6 minutes.
Test AF1 revealed that a pre-float stage does not improve flotation performance, and that there is an activation mechanism occurring within the pulp chemistry, considered at this preliminary stage to likely be related to the partial weathering of the core samples and will need to be further investigated.
AF4 is the next test underway, investigating the ability to separate into two different concentrates. The first photograph (Fig. 1a) represents the initial Lead Rougher flotation stage and indicates good lead mineralisation in the froth. The second photograph (Fig. 1b) represents the Zinc Rougher stage and shows reasonable zinc mineralisation.
For further details of the tests see Appendix A - JORC Table 1 Section 4 (see link below).
KEMPFIELD ECONOMIC FEASIBILITY
Argent is aggressively pursuing Kempfield economic feasibility through several programmes currently directed at the following goals:
- Increasing the Kempfield mineral resource - through the infill drilling programme that Argent is designing and executing for validation of the significant Exploration Target estimate announced 8 November 2017;
- Optimising plant feed grades - through a combination of (i) improving grades where possible through the above exploration, aided by the new 3D geological model for wireframing identified mineralisation, and (ii) 'high grading' the selection of material for milling and processing; and
- Optimising metal recoveries - through the continuing metallurgical testing programme, with the preliminary results reported in this announcement exceeding historical assumptions.
Significantly improved zinc prices have further boosted the project economic potential, as reported by the Company in the 24 August 2017 announcement - 'Argent to Increase Zinc Assets as LME Price Hits 10Y High'.
With the assistance of specialists Australian Mining Design and Development Pty Ltd (AMDAD), Argent has developed a detailed [conceptual] financial model to guide ongoing decision making on the key elements of the project over which it has control, as the Company continues to advance Kempfield toward the goal of economic viability, and ultimately - production.
The comprehensive financial model incorporates the substantial data obtained through the Company's feasibility study work conducted during approximately 2011 to early 2013. The available data includes mine design options based on open cut mining, as well as infrastructure and environmental planning information. The Company continues to update the model as new data becomes available, for ongoing analysis.
About the iterative metallurgical testwork process
Argent is conducting the metallurgical testwork as an iterative process in order to develop the most efficient process flowsheet for extracting saleable metals concentrates from Kempfield-specific deposit material.
This is standard practice for polymetallic projects such as Kempfield.
As the results are received for each group of tests in the series, these are analysed and used for the design of the subsequent group of metallurgical tests, and so on, until a conclusive result is obtained.
About the next steps in the current testwork series
Argent is conducting the following further work to resolve the key identified key challenge of lead and zinc separation, based on the metallurgical engineer's recommendations:
1. Pursuing a series of tests with varying reagent regimes;
2. Conducting tests with regrinding lead and zinc rougher concentrates followed by cleaning flotation steps; and
3. Reviewing the mineralogy of the process products to determine distribution of the mineral components.
All of these tests are utilising the existing drill core prepared and stored in the AMML freezers as described on page 2 of this announcement.
The Company may conduct further testing on samples obtained through the resource infill drilling programme.
To view tables and figures, please visit:
About Argent Minerals Limited
Argent Minerals Limited (ASX:ARD) is an Australian publicly listed company with a 100% interest in a silver/gold project at Kempfield NSW. Work is underway on the preparation of an EIS and a feasibility study for the first stage of the project which will involve heap leaching some 8.8 million tonnes of mainly oxide and transitional material to produce over 9.5 million ounces of silver and 15,000 ounces of gold over a 5 year mine life. Argent is also earning up to a 70% interest in two other NSW projects - gold at West Wyalong and base metals at Sunny Corner.
Chief Executive Officer
Argent Minerals Limited