Further metallurgical test work on Lindian Resources’ high-grade sample ores from the Bouba conglomerate bauxite deposit at its Gaoual bauxite project in Guinea has come up trumps again. The company says digestion test work following up on recent positive results from dry screening of the Bouba ores showed they were suited to both low temperature and high temperature digestion settings in Bayer process alumina refineries.
Digestion test work was carried out by Bureau Veritas in Perth on the high-grade bauxite sample ores beneficiated by the primary screening test work. Importantly, with the nuisance silica impurity grade having dropped like a stone in the screened high-grade conglomerate ores, Lindian says the reactive silica percentage levels achieved in the digestion test work are now in line with the highest quality bauxites being mined in and exported from Guinea.
The Gaoual project’s Bouba conglomerate bauxite deposit hosts an indicated open-pittable resource that contains a higher-grade block of ore totalling 83.8 million tonnes going an average grade of 51.2 per cent aluminium oxide and 11 per cent silica.
According to Lindian, a simple screening process now has the capacity to significantly upgrade the Bouba ore quality and the aspiring West African bauxite developer has every reason to be hopeful.
Its recently completed screening test work program sought to determine the potential for upgrading of the conglomerate bauxite ores containing high-grade aluminium oxide and a high silica content, to ores consisting of higher-grade aluminium oxide and low-percentage silica through the removal of fine-grained material.
The screening of the high-grade Bouba conglomerate bauxite ore samples – sourced from a handful of test open pits – saw the aluminium oxide grade climb from 53.8 per cent to an impressive 58.4 per cent and the silica grade fall from 9.8 per cent to 2.8 per cent, with minimal loss of tonnage.
Generally, the more silica in bauxite ores, the higher the amount of caustic soda required in the refining process and the higher the loss of aluminium oxide content. Lindian’s dry screening test work on the conglomerate bauxite ores returned a coarse component of 87.2 per cent of the mass volume total.
Senior Geologist Consulting to Lindian, Mark Gifford said recently: “The screening test work … has provided conclusive support to the assumption that by removing the fines material from the conglomerate ores the resultant bauxite would dramatically improve in quality.”
ASX-listed, Perth-based Lindian is hoping to advance a potential low CAPEX near-term pathway to bauxite production in Guinea, initially via its smaller Woula deposit while simultaneously looking to advance the much larger Gaoual and Lelouma bauxite projects.
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By Matt Birney
