Abstract
The aim of this paper was to characterise Mt Weld Nb–Ta ore and assess the amenability of the ore to gravity and magnetic separation, flotation, and caustic and acid leaching. The Mt Weld niobium deposit occurs in altered carbonatites in Western Australia where Sr pyrochlore and ferroniobate were the major primary Nb–Ta containing minerals. Primary apatites, pyrochlores and niobates were altered to form micrometre to submicrometre size crandallites. The fine crandallite particles were often clustered to form larger aggregates, mixed or cemented with fine niobates (up to 20 μm) and coarse (up to 200 μm) ilmenite. This study showed that the ore was not suitable for gravity concentration, magnetic upgrading and flotation due to fine particle size. Although the fine particle size was advantageous for chemical treatment and ore responded better to caustic and acid leaching, the chemical treatment alone was well short of providing a commercial grade niobium concentrate containing 60% Nb2O5+Ta2O5. It is concluded that upgrading Mt Weld ore to a commercial grade concentrate would require a combination of physical and chemical treatments where physical treatment is used to remove coarse ilmenite and chemical treatment to dissolve impurities associated with the fine ore.
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