rejig

A rejig in ore processing means passing broken or crushed ore back through a jigger (a type of vibrating separation device) to recover material that was missed or misclassified in the first pass. The jigger itself is a tank or box where ore particles are subjected to pulsating water flows or mechanical vibration, causing heavier mineral particles to settle while lighter gangue is carried away. Rejigging happens when initial screening and separation proves incomplete.

The process relies on differences in particle density and settling behavior. Minerals of interest, like cassiterite, magnetite, or gold-bearing particles, settle faster than waste rock under the right conditions. A rejig typically involves feeding the jig again at the same screening stage or a slightly different one, sometimes with adjusted water flow rates or deck angle to encourage better separation. Multiple passes through a jigger increase recovery but also increase processing time and water consumption.

When and why rejigs occur

Rejigging becomes necessary when plant operators suspect incomplete liberation or when assay results from tailings show unacceptable losses of target mineral. It is also standard practice for difficult ore types with similar density distributions between valuable minerals and waste, or when ore grain size is inconsistent. Fine-grained ore below about 500 microns becomes harder to separate cleanly, making rejigs more common in tin and tungsten operations than in iron ore circuits.

The term itself follows the pattern of other mining operations: jigging is the primary action, and rejig simply means doing it again. It is not a separate piece of equipment but a scheduling decision made by process controllers based on metallurgical performance. In modern plants, this decision is often prompted by density, particle size, or moisture readings rather than a routine repeat. The cost of rejgging must be weighed against the value of recovered minerals and the risk of further contamination from recirculated material.