Material segregation is one of the most overlooked physical factors affecting heap leach performance. Segregation occurs when coarse and fine particles separate during handling, conveying, transfer or stacking. The resulting heap may contain zones with significantly different permeability, solution distribution and leaching behaviour.
Heap leaching depends on both chemistry and fluid flow. Even when ore is mineralogically suitable for leaching, poorly distributed particle sizes can create preferential flow paths, ponding zones or under-irrigated areas.
Research and industry experience consistently identify permeability and solution movement as critical drivers of heap performance.
Sources note that fines, clay content, particle size distribution and heap construction practices strongly influence permeability and recovery potential.
Why segregation occurs
- Differences in particle size, density and shape.
- Large drop heights at transfer points.
- Stockpile formation and reclaiming.
- Truck dumping and dozer spreading.
- Excessive conveyor discharge velocities.
- Agglomerate breakdown after conditioning.
What segregation looks like in a heap
Coarse particles tend to roll further and accumulate in some zones while fine particles accumulate in others. This creates a heterogeneous ore body rather than a uniform leach reactor. Fine-rich zones may compact and restrict flow, while coarse zones may provide rapid preferential channels.
Why segregation matters
Segregation changes permeability. Low-permeability zones may wet slowly or not receive solution uniformly. High-permeability zones may receive disproportionate flow. This can reduce effective ore contact and create variable recovery across the heap.
Relationship between segregation and agglomeration
Agglomeration is often used to attach fines to larger particles before stacking. When successful, it helps reduce fines migration and maintain a more stable particle distribution.
However, agglomeration does not eliminate segregation and poor handling practices can still damage agglomerates during conveying and stacking.
The role of stacking systems
Heap construction methods influence segregation behaviour. Conveyor-based stacking systems can offer greater control over feed placement, transfer points and discharge conditions than repeated truck dumping and dozer spreading alone.
However, no stacking system completely prevents segregation. Transfer design, drop height, feed consistency, chute geometry and operating practices remain important.
Practical methods to reduce segregation
- Maintain consistent crusher product sizing.
- Apply agglomeration where justified by test work.
- Minimise unnecessary transfer points.
- Reduce excessive drop heights.
- Optimise chute and transfer design.
- Use controlled stacking procedures.
- Monitor heap permeability and drainage behaviour.
- Consider ore blending where variability exists.
Frequently Asked Questions
Here are some common questions we get asked at Carmaky.
What is material segregation?
The physical separation of coarse and fine particles during handling and stacking.
Does segregation affect recovery?
It can influence permeability and solution flow, which can affect how effectively ore is contacted by leach solution.
Can agglomeration eliminate segregation?
No. Agglomeration can reduce fines migration but does not guarantee elimination of segregation.
Can conveyor stacking reduce segregation?
Controlled conveyor stacking may reduce some segregation mechanisms but does not remove the need for good ore preparation and transfer design.
Conclusion
Heap performance begins before irrigation starts. Ore preparation, agglomeration, conveying and stacking collectively influence particle distribution within the heap. While metallurgical performance is often discussed in terms of chemistry and recovery, the physical arrangement of ore can be equally important. Understanding and managing segregation helps support more consistent permeability, solution distribution and heap performance.
Related resources: heap leach stacking systems · Heap Leach Resource Centre