Heap leaching of manganese-containing ores

1. A method for the heap leaching of manganese-containing ores, the method characterised by the steps of:

(i) beneficiating the manganese-containing ore and separating the beneficiated ore into a coarse ore fraction and a fine ore fraction;

(ii) combining the fine ore fraction with a sulfide ore material to produce a combined ore fraction;

(iii) stacking the combined ore fraction to form at least one heap; and

(iv) applying a lixiviant to the heap to produce a pregnant leach solution (PLS) containing dissolved manganese values,

wherein the lixiviant is added to the or each heap in the presence of soluble iron.

2. The method according to claim 1 , wherein the fine ore fraction has a particle size of less than about 6 mm.

3. The method according to claim 1 , wherein the beneficiating step uses a dense media separation (DMS) plant.

4. The method according to claim 3 , wherein the coarse ore fraction includes a lump ore fraction resulting from the DMS plant.

5. The method according to claim 1 , wherein the ratio of manganese-containing ore to sulfide ore material in the combined ore fraction is within the range of about 3:1 to 8:1.

6. The method according to claim 1 , wherein the sulfide ore material is a waste sulfide ore material.

7. The method according to claim 1 , wherein the method includes either an agglomeration step after step (ii) or an agglomeration step is used to effect the combination of the fine ore fraction with the sulfide ore material in step (ii).

8. The method according to claim 7 , wherein the agglomeration step is performed using one or more of acid, water, or PLS.

9. The method according to claim 7 , wherein sulfuric acid is used in the agglomeration step, and the acid concentration is within the range of about 5 to 15 g/L.

10. The method according to claim 7 , wherein the agglomeration step includes the use of a binding agent selected from lime, cement or a polymer binding agent.

11. The method according to claim 1 , wherein the lixiviant of step (iv) is provided in the form of sulfuric acid at a concentration within the range of about 40 to 80 g/L.

12. The method according to claim 1 , wherein the soluble iron is contained within the lixiviant in the form of ferrous iron.

13. The method according to claim 1 , wherein the soluble iron is added either as ferrous sulfate or is added by addition of PLS.

14. The method according to claim 1 , wherein the concentration of soluble iron added to the heap with the lixiviant is in the range of about 5 to 20 g/L.

15. The method according to claim 1 , wherein the PLS is recirculated through the heap until the manganese content rises to within the range of about 30 to 80 g/L.

16. The method according to claim 1 , wherein the pH of the heap is within the range of about 1.5 to 3.5.

17. The method according to claim 1 , wherein the method of the present invention also includes the further steps of:

(v) drawing a bleed stream from the PLS and raising the pH of said stream to at least about 5.5 to produce a neutralised PLS; and

(vi) directing the neutralised PLS to a solid/liquid separation step to separate iron oxides and/or hydroxides from the neutralised PLS.

18. The method according to claim 17 , wherein the pH of the neutralised PLS is within the range of about 5 and 6.

19. The method according to claim 17 , wherein the method of the present invention still further includes the step of:

(vii) directing an overflow of neutralised PLS from the solid/liquid separation step to an evaporation pond to crystallise manganese sulfate.

20. The method according to claim 19 , wherein the overflow of neutralised PLS is directed to a purification step prior to the evaporation pond.