Modern Mining April 2021

concentrate is at an advanced stage. Previous test work focused entirely on the differences in magnetic susceptibility between CGM and cassiterite, since pure cassiterite is non-magnetic whereas CGM are weakly magnetic. However, the test work found that a portion of the cassiterite had a magnetic response similar to the CGM. Further investigation found that inclusions, trace elements and surface effects are the probable cause of the overlapping magnetic response. Preliminary test work focused on roasting and leaching the company’s concentrate to suppress the magnetic response of cassiterite and this process has deliv- ered encouraging results. Further investigation and process flow development aims to optimise a combination of leaching and roasting techniques to improve the efficiency of magnetic separation and provide a separate high value CGM by-product. Lithium metallurgical investigations The primary lithium oxide-bearing mineral present in the orebody at Uis has previously been identified through XRD analysis and thin section investigation as petalite. The 2019 exploration drilling campaign yielded anomalous lithium oxide intersections that included 86,51 m grading at 1,22% Li2O (drill hole V1V2017) and 109,32 m grading at 0,97% Li2O (drill hole V1V2010). Test work for the production of a petalite con- centrate by-product has been initiated. Preliminary heavy liquid separation (HLS) tests, utilising drill core samples, provided positive indications that a saleable petalite concentrate can be produced. The petalite is naturally low in deleterious compounds, in particular iron oxide (Fe 2 O 3 ) and potassium oxide (K 2 O), and may be suitable feedstock for the produc- tion of technical grade lithium concentrate for the glass and ceramics industries. The Company will also investigate the suitability of its petalite concentrate for the production of battery-grade lithium products in this work programme. Petalite is the lowest density mineral pres- ent within the ore mined at Uis, whereas, Tin and Tantalum-bearing minerals represent more dense fractions. Investigations will focus on incorporating technologies and methods currently employed at the processing plant, including dense medium sepa- ration (DMS) and magnetic separation. The petalite characterisation will incorporate HLS of bulk samples taken from run-of-mine feed, followed by concen- trate cleaning through magnetic separation, and ultimately pilot-scale processing runs. Ore processing metallurgical investigations An investigation into the pre-concentration potential of tin, tantalum, and lithium oxide-bearing minerals using sensor-based ore sorting has commenced. This process involves the use of X-ray, or hyperspectral

Test work for a tantalum concentrate is at an advanced stage.

imaging technologies, to characterise ore particles and manually or pneumatically sort them. The methodology is suitable for ore streams of a relatively high top size (typically 20 to 80 mm) and has the potential to allow mineral concentration or waste rejection early in the process, thereby increas- ing downstream processing capacity and reducing processing costs. Initial test work will investigate the potential applicability of various X-ray imaging meth- ods and sensors at Uis. Furthermore, successful discrimination of minerals may be followed by bulk material tests. 

Lithium oxide concentrate test work is progressing to a second stage.

Key takeaways  Uis has a JORC (2012)-compliant measured, indicated and inferred min- eral resource estimate totalling 71,54-million tonnes of ore containing 95 539 tonnes of tin (Sn) metal at a grade of 0,134% tin  In addition, the mineral resource estimate includes tantalum and lithium oxide  The presence of significant tantalum and lithium oxide mineralisation cre- ates an opportunity for the development of additional revenue streams  The company is advancing a metallurgical test work programme aimed at developing the process flow to efficiently produce tantalum and lithium oxide by-products

April 2021  MODERN MINING  15