Sovereign Metals reports the discovery and successful metallurgical separation of high grade rutile (TiO2) from within the soft, saprolite-hosted graphite deposit at Malingunde in Malawi.
Central Africa – Sovereign Metals is focused on future low-cost production of high quality graphite concentrates at Malingunde.
Recent test work highlighted the potential to produce rutile as a valuable co-product from
the graphite tailings.
Importantly, clean rutile concentrates are produced via a simple process flow sheet using traditional flotation for graphite and typical mineral sands separation methods.
“Sovereign Metals is focused on developing the world-class, low-cost graphite operation at Malingunde,” comments Sovereign Metals MD Dr Julian Stephens.
“The discovery of rutile-leucoxene as a potential co-product, produced from the graphite tailings via a simple process flow sheet provides the potential for additional revenue streams and enhanced project value.
“Sovereign Metals intends to undertake further studies to advance work on this discovery, without compromising the focus upon the development of graphite operations at Malingunde,” he continues.
During recent chemical analyses of bulk graphite metallurgical samples for flotation test-work from Malingunde it was noted that TiO2 levels were significantly elevated.
It was hypothesised that the elevated TiO2 may be due to the presence of rutile and/or leucoxene, as the company had previously identified rutile within its Duwi graphite deposit, some 30 km to the north-east of Malingunde.
Rutile (TiO2) is a highly sought after, high grade titanium feed source with concentrates currently fetching ~US$900 – 1,050/tonne and projected to reach long term pricing of US$1,250/tonne (FOB) by 20192 Leucoxene is priced at a discount to the prevailing rutile price, generally based on TiO2 content.
Test work – Sovereign Metals undertook a programme to test the hypothesis that elevated TiO2 levels at Malingunde were due to the presence of rutile and /or leucoxene, and if so, whether it may be recoverable as a saleable coproduct to the graphite operation.
Assay of drill samples – A total of 5 sections of drill core (MGDD0003-MGDD0007) were selected for multi-element analysis and totalled 80 samples.
These samples were also selected to represent a range of graphite grades from 0 to 30% and to cover all of the different weathering zones identified at Malingunde.
Holes MGDD0004 and MGDD0005 also showed similarly high TiO2 values, however, these sections are mainly hosted in more competent saprolite and saprock and hence are not considered economically important.
Overall, results show a minimum of 0.75%, a maximum of 2.52% and an average of 1.33% TiO2 content.
There appears to be a slightly negative correlation of TiO2 to graphite, total graphitic carbon)(TGC) with a clearer negative correlation below about 10% TGC.
TiO2 appears highly enriched in soil (SOIL), and possibly enriched in the near surface ferruginous pedolith (FERP), both in areas where there is little to no graphite.
Heavy liquid separation – Heavy liquid separation (HLS) work was carried out at AML in Perth on 10 selected samples, making up the key MOTT and SAPL zones, of the 80-sample suite assayed and reported in the preceding section.
The samples were subject to a standard deslime prior to the HLS work. Slimes range between 17% and 34% with higher slimes recorded in the near surface mottled zone.
The encouraging results from the HLS work, where recovered rutile-leucoxene grades ranged between 0.5% and 0.9%, led Sovereign Metals to initiate a programme on bulk samples at AML in Perth.
This programme involved taking two bulk composite samples split from graphite flotation test-work tailings.
These were then subject to a primary wet table separator, with the primary middlings also subject to a secondary wet table separation for both samples.
XRD mineralogy was then undertaken on 3 splits (concentrate, middlings and tailings) for each of the South and North Composites (6 in total).
TGC by Eltra and Na-peroxide fusion ICP OES/MS was conducted on the 6 splits.
Electrostatic (HTR) separation of the combined concentrate and middlings fraction for the North and South composites was completed.
Finally, magnetic separation on the HTR middlings and conductor for the South composite, and on the conductor for the North composite was completed.
Rutile is a relatively common accessory mineral in reduced paragneisses and schists such as these in central Malawi.
However, the occurrence of potentially economically recoverable grades of rutileleucoxene
at Malingunde and throughout the Lilongwe Plains area (mainly controlled by Sovereign) hosted within saprolite appears relatively unique.
The test-work program has shown that overall recovered grades of TiO2 from raw ore into rutile-leucoxene concentrates, was 0.86% (South Composite).
Concentrates produced to date from these initial sighter tests highlight the potential for
the commercial production of leucoxene concentrate as a co-product produced from the graphite tailings.
Further work needs to be undertaken to determine if high grade +95% TiO2 rutile concentrates can be produced from the Malingunde tailings material.
Recovery of rutile-leucoxene from Malingunde tails should be further investigated as a possible, future extension to the proposed graphite operation at Malingunde.
Additionally, the regional rutile-leucoxene potential would seem substantial and is economically interesting for a number of reasons.