Mining and Mineral Processing
Domain scope
Mining and Mineral Processing tests how an orebody becomes a saleable product. Expect questions on cut-off grade, mine dilution, comminution, separation selectivity, and metallurgical balances. The exam rewards candidates who can link geological grade, mining method, and plant performance numerically.
Core rules
- Cut-off grade is the grade at which the value of contained metal equals mining, processing, and rehabilitation costs; material below it is waste if no alternative use.
- Dilution lowers mill feed grade by mixing waste into ore; it must be included before calculating metal output.
- Stripping ratio is waste tonnes per ore tonne. It affects cut-off grade because waste must be hauled and rehabilitated, so a higher strip ratio raises the cut-off.
- Comminution increases liberation but consumes energy; overgrinding creates slimes that hurt flotation and dewatering. Gravity separation relies on density contrast, magnetic separation on susceptibility, and leaching on solubility.
- A separation unit is judged by concentrate grade and recovery, not by one alone. Recovery = contained metal in concentrate ÷ contained metal in feed.
- Use consistent units and dry tonnes for mass balances; water is tracked separately.
Worked example
A plant treats 100 t/h of ore grading 2.0% Cu. It produces a concentrate grading 20% Cu and tailings at 0.2% Cu. Let C be concentrate mass. Copper balance: 100×0.02 = C×0.20 + (100−C)×0.002. Thus 2 = 0.20C + 0.2 − 0.002C, so 1.8 = 0.198C and C = 9.09 t/h. Copper in concentrate = 9.09×0.20 = 1.818 t/h. Recovery = 1.818/2.0 = 90.9%. The tailings carry 0.182 t/h Cu, confirming the balance.
Traps
Do not call 20% Cu “recovery”; it is concentrate grade. Do not calculate recovery from feed tonnes alone. Do not ignore dilution or tailings grade. Do not mix wet and dry tonnes. Do not assume flotation liberates all minerals.