In 2018, Sovereign reported that it had successfully recovered rutile concentrates from tailings at the Malingunde graphite project (ASX announcement 14th August 2018). This work showed rutile was the dominant TiO2 mineral and in concentrates it was shown to be generally present as discrete, clean and liberated grains. Overall, this program demonstrated the ability to produce rutile concentrates from the soft saprolite material using typical mineral sands processing methods.
Sovereign has since identified significant rutile mineralisation over large areas within its 100%-owned Malawi ground holdings. Rutile occurs in soft, free-dig saprolite down to approximately 25m depth with grades also particularly enriched in the upper 5m or so of the weathering profile.
Rutile mineralisation shows no discernible chemical, spatial or geological relationship to graphite mineralisation.
Almost all known commercial rutile deposits occur as placer accumulations with the original source rocks most commonly being metamorphosed sedimentary rocks known as paragneisses1. These bedrock sources in most cases contain relatively low grades of rutile, although they are often exposed over vast areas. When eroded, this material is washed into large water bodies (oceans, lakes, rivers) where the heavy minerals are concentrated into placers by wind and water action.
In Malawi, Sovereign controls a very large area underlain predominantly by paragneiss rocks which appear to be highly enriched in rutile compared to most other similar terranes globally. Additionally, the weathering process has further concentrated the rutile near surface as lighter and more soluble minerals have been transported away. Overall, this has created an unusually high concentration of rutile in the residual weathering profile. The result is a 20-25m thick “blanket” of rutile mineralisation over significant areas all hosted within soft, friable and free-dig saprolite material.
As a comparison, Iluka Resources controls the world’s largest and highest grade rutile mining operation in Sierra Leone. The original source rock for these deposits is also a paragneiss known as the Kasila Gneiss. These deposits were formed as a result of weathering and erosion of the Kasila Gneiss which outcrops in areas adjacent to the mining operations2. The rutile grains have been transported only a short distance by alluvial action and deposited into placers. This is reflected by the relatively low levels of sorting, wide grain size distribution and high angularity of the rutile grains. Rutile from Sierra Rutile is considered a premium product due to low impurities and its high angularity. This product is favoured by consumers for its potential to create a higher-quality end product with less waste 3.
Initial assessments by Sovereign’s geological team indicate substantial potential for saprolite-hosted, residual rutile deposits across the Company’s significant ground position in Malawi. Initial test work demonstrated the potential to recover rutile via typical mineral sands processing flow-sheets. Visual examination shows high grain angularity related to the fact that the rutile has formed in situ and has not been subject to placer transport. The high angularity is a favourable feature for rutile feedstocks as it denotes a larger grain specific surface area which results in faster and more efficient reactivity in the chlorination process used for pigment production.
An initial sighter metallurgical test-work program was undertaken on a 180kg sample of saprolite-hosted rutile from the Wofiira prospect at a well-known mineral sands laboratory in Perth, Western Australia. The test-work program, which was focused on generating saleable product specifications, demonstrated that a high-quality commercial rutile product can be produced using conventional mineral sands processing methods. The recovered rutile grade from in-situ was 1.16% produced in a +38µm to -250µm size fraction. Test work is ongoing in order to improve rutile recoveries and to determine if other valuable heavy minerals can be recovered as by-products.Results from the initial metallurgical program show that Sovereign’s rutile product specifications meet market requirements with many parameters at best-in-class levels. Standout attributes include;
The titanium dioxide (TiO2) minerals rutile, leucoxene and ilmenite are the principal feedstock for pigment production. Natural rutile is the highest-grade feedstock for manufacturing TiO2 pigment and producing titanium metal. Titanium pigments are used in paints, coatings and plastics. Titanium also has specialty uses including welding electrodes, commercial aerospace and military applications.
According to the world’s largest rutile producer, Iluka Resources Limited (“Iluka”), global supplies of natural rutile are in structural deficit5. Iluka sees continued growth in demand for high-grade titanium feedstocks over 2019 and is physically unable to satisfy all requests for feedstock in the high-grade titanium segments of the market.
Historically, all titanium feedstock prices including rutile prices have followed US pigment prices with a six to 12-month lag. However, since 2017, as natural rutile supply tightness has emerged, rutile prices have decoupled from their historic relationship with US pigment prices. For the 15 months following the end of 2017, US pigment prices have increased by 4% whereas the rutile price has increased by 21% 5.
Iluka’s average rutile prices in the first half of 2019 exceeded US$1,100/t with expected price increases of 6-8% based on tight supply conditions coupled with strong demand from the pigment and welding markets 6.