Nemex Resources Limited announced results from initial metallurgical test work performed on three representative potential direct shipping ore (PDSO) samples from across the Boulere resource area, Telimele Iron project, west Guinea.
The preliminary test work indicates that, based on the samples tested, a high-proportion (approximately 55–75%) of the T1 Telimele mineralization (that the company has recently announced as an inferred resource of 16.8 million tonnes @ 55.1% Fe) is blocky in nature and only requires a simple on-site crush and screen process to generate a 'lump' product of >60% Fe for transport and sale to the iron ore market.
The finer grained 'Fines' product (-6.3mm) shows, as expected, a lower Fe grade product characteristic but the davis tube recovery (DTR) testing suggests that there is a strong possibility that this product can be upgraded to a marketable Fe product using a beneficiation process, likely to be magnetic separation based on the preliminary DTR results (and possibly a gravity separation process that has yet to be undertaken). Further beneficiation test work on the fines product is planned.
Nemex Resources reiterates that its focus at this stage is to advance the mining of the T1 mineralization using a simple crush and screen process prior to export, and to investigate, at a later stage, the T1 Fines, the T2 and T3 mineralization.
Peter Turner, managing director of Nemex Resources, said, "These very encouraging initial metallurgical test work results indicate that a DSO lump product can be produced from the Boulere resource area, affirming Nemex’s strategy to mine a product that does not require beneficiation prior to export.
"Pricing forecasts will be incorporated into the Concept Study that will explore early cash-flow by mining the DSO, using either of two nearby Governmentowned, multi-user rail lines to deliver the product to port. This study will be completed by the end of March."
Metallurgical test work
The maiden mineral resource estimate for the Boulere prospect of 258 MT @ 37.3% Fe using a 30% lower cut-off grade was announced on January 10, 2013. This resource includes 16.8 MT @ 55.1% Fe of domain T1 ironstone.
The metallurgical samples, each weighing in excess of 200kg, were collected using a PC220 excavator from pits at several sites over the Boulere resource area. Although these three T1 metallurgical samples are representative of the T1 unit, additional test work is required on core samples from a greater area of the resource to confirm this initial metallurgical work.
The objective of this test work was to provide preliminary information to determine the characteristics of the T1 unit and to particularly define whether the T1 unit could sustain a direct shipping ore (DSO) operation without the need for expensive, on-site beneficiation. The company is encouraged from the results of this initial test work and it provides the impetus for further work in collection of core samples across the resource, and to determine if the conclusions presented herein (that the product is a DSO Fe product) can be extrapolated across the entire, current resource.
All test work was performed at the Bureau Veritas mineral processing laboratory in Canning Vale, Western Australia.
Testwork for Lump product (-35 +6.3mm)
A lump product comprises irregularly sized lumps of iron ore between 6.3mm and 35mm in diameter that can be charged directly into a blast furnace (avoiding the need to sinter or aggregate iron ore fines). Lump currently trades at a premium to fines.
The conventional test work to determine the quantity of Lump that can be yielded from iron ore mineralization is the drop tower test, where a large (~100 kg) sample is dropped from a nominal height (in Nemex Resources's case, five times from a height of 17m) to determine its ability to break down.
The three, +200kg samples of Nemex Resources were dried at 65°C then screened at 50mm. The oversize blocks were sent away for size-reduction then recombined and homogenized with the rest of the sample. The sample was then control-crushed to 100% passing 35mm before being subjected to the drop tower tests.
The results show that each sample produces a large proportion of lump mass comprising 57–74% of the total sample mass post-drop tower testing. Lump product assay results for each sample show Fe grades >60% Fe in all cases and – importantly – an increasein Fe grade of 1–3% over the drop tower feed grade.
Fines product (-6.3mm)
A fines product is the baseline product in the iron ore market. Fines require sintering – the iron ore fines material is mixed with coke and fluxes and with the application of heat is converted into large porous lumps suitable for direct charging into the blast furnace. The chemistry of the -6.3mm fraction post-drop tower testing shows Fe ranges of 55.6–58.6% Fe.
Davis tube recovery results on Fines (-6.3mm)
Each Fines (-6.3mm) sample from the drop tower test was subjected to a davis tube recovery (DTR) test, to determine the possible product upgrade using a magnetic separation process. The results show a significant improvement of the product chemistry of the magnetic concentrate in terms of Fe, Al2O3, SiO2, P and S.
Fe values of the magnetic concentrate report between 61.5% Fe and 63.6% Fe, an increase of between 8–13% over the assayed head grades of the Fines samples.
Two of the three samples show >70% mass recovery reporting to the magnetic concentrate. Sample NGX1002 had a lower mass recovery of 22.7%.
Future test work will review the amenability of the Fines samples to gravity separation, with the aim of increased iron recovery. This will include a review of a de-slimes stage for clay removal.
Further metallurgical test work
HQ3 core drilling is planned over the Boulere resource area in the second half of 2013. The core will provide further metallurgical information over the resource area as the company moves closer to reserve estimation.
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