AIM-listed tin hopeful AfriTin Mining has completed additional dense medium separation test work for the upgraded phase 1 processing plant at its Uis tin project in Namibia, which is due to be operational during the fourth quarter of 2018.
Namibia – Test work has been conducted by PESCO, a dense media separation (DMS) expert in South Africa, on a bulk sample of 2 t, which is a potentially representative sample of the V1 and V2 pegmatite bodies. These pits were previously identified by AfriTin as priority targets to supply feed to the upgraded processing plant at Uis.
The results showed over 85% stage-1 tin recoveries in 2.66 g and 2.62 g/cm3 cut densities; up to 91% recoveries in second-stage separation (at a cut density of 2.9 g/cm3); and over 60% tin dioxide in the final concentrate following the removal of muscovite.
These initial results confirm the beneficiation potential of the Uis pegmatites to produce a high-grade tin concentrate from a coarse run-of-mine feed. Further test work and alternatives are ongoing to potentially enhance these results and to further prove the beneficiation capability of the fine fraction arising through the crushing of the ore.
“The excellent recoveries achieved in this bulk test work highlight the potential of concentrating mined material, to produce the output of tin concentrate from a significant tin and multi commodity deposit, says AfriTin Mining CEO Anthony Viljoen.
“The completion of this test work has been a key element of the final design for our Phase 1 processing plant at the historic Uis mine and bodes well for the expansion during Phase 2 of the project which envisages a full-scale production facility of 3 Mtpa of ore,” Viljoen adds.
Summarised results of test work performed
A two-stage DMS separation test circuit was implemented as follows:
- Stage 1: A pre-concentrating stage to maximize cassiterite recovery while effectively reducing mass for downstream processes. The relative densities tested ranged from 2.62 to 2.74 g/cm3.
- Stage 2: A concentrating stage to increase the product’s tin grade. Concentration was carried out on Stage 1 concentrate material at three individual densities, these being 2.9 g/cm3, 3 g/cm3 and 3.1 g/cm3.
The results obtained from the Stage 1 test work indicate that the anticipated run of mine material behaves very well for pre-concentrating the material through the DMS circuit. The results indicate that the plant will be able to achieve an 80% mass reduction of mine material whilst retaining 90% of the tin. This allows for lower capital costs in a smaller back end to the primary circuit.
Based on the successful results of the Stage 1 test work, a pre-concentration step was conducted at a density of 2.65 g/cm3, followed by a series of tests to investigate the density at which to conduct the second stage DMS operation.
The results of Phase 2 further indicate that DMS is able to generate a higher-grade concentrate in the 6.5 m fraction, with further test work currently underway to confirm the optimal liberation size and separation density for this stage.
The bulk of the gangue material that reported to the product at a separation density of 3.1 g/cm3 is muscovite. Following the removal of this muscovite (which is being investigated as a potential by-product), a final concentrate grade in excess of 60% is produced in the coarse fraction.