Factors affecting mine viability — AQA A-Level Environmental Science

Factors affecting mine viability encompass the technical, economic, and environmental variables that determine whether a mineral deposit can be categorised as an exploitable reserve rather than a sub-economic resource. Key geological parameters include deposit depth, ore grade, chemical composition, presence of associated valuable or toxic minerals, and structural stability of host rocks.

Within AQA A-Level Environmental Science, this topic integrates physical geology with industrial economics and ecological protection. Students evaluate how market fluctuations, transport access, energy inputs, and environmental mitigation requirements dictate whether extraction proceeds via open-cast, underground, or in-situ leaching methods.

• →Cut-off ore grade: the lowest purity of ore that can be extracted at a financial break-even point, dictated by price and technology.
• →Overburden stripping ratio: the volume or mass of waste material that must be removed per unit of usable ore in surface mining.
• →Chemical form and purity: the mineral lattice (e.g. oxide vs sulphide) determines smelting energy, hydrometallurgical reagents, and atmospheric emissions.
• →Hydrological conditions: water table depth dictates pumping operating costs and risks of acid mine drainage (AMD) formation.
• →Ancillary infrastructure: proximity to transport routes (rail, deep-water ports), industrial water sources, and national power grids determines capital expenditure.

• Defines overburden as the material above the ore body that must be removed to access it.
• Explains that thick or hard overburden increases stripping and excavation costs and can reduce viability.
• Explains that hydrology, including groundwater inflow and permeability, affects pumping, dewatering and water-treatment costs.
• Compares two sites with different overburden and hydrological conditions and judges which is more viable and why.

• 💡Separate overburden and hydrology into distinct cost factors in your answer.
• 💡Use a comparison of two sites to show how each factor changes viability.
• 💡Quantify where possible, for example thicker overburden meaning more waste rock per tonne of ore.
• 💡Distinguish clearly between capital expenditure (CapEx, such as shaft sinking and processing plant construction) and operational expenditure (OpEx, such as diesel, explosive use, and water pumping).
• 💡Integrate environmental mitigation costs into viability calculations; include tailings dam stabilization, acid mine drainage treatment, and post-closure site restoration.
• 💡Use accurate quantitative terms such as 'grade decline', 'dilution', and 'stripping ratio' rather than subjective descriptors like 'good rock' or 'easy digging'.

• Confuses overburden with the ore body itself; keep overburden as the waste material above the ore.
• Ignores water management costs; include pumping, dewatering and treatment when assessing hydrology.
• Assumes geology affects only extraction speed; link geological and hydrological conditions to specific costs and risks.
• Confusing mineral resources with mineral reserves: a resource is total mineral estimated to exist, whereas a reserve is the portion legally and economically viable to extract today.
• Assuming higher market commodity prices always cause immediate mine openings: significant capital expenditure, lead times, and environmental impact assessments delay responses by years.
• Believing underground mining is always preferred when ore is deep: if the host rock is heavily faulted or porous, ground support and dewatering costs may make shaft mining impossible.

1. 1Day 1-3: Memorise key quantitative definitions: cut-off ore grade, stripping ratio, reserves versus resources, and calculate basic break-even thresholds.
2. 2Day 4-6: Build a comparative matrix linking geological characteristics (depth, chemical form, hydrology) to specific extraction costs and operational limitations.
3. 3Day 7-9: Analyze past AQA exam questions on environmental legislation, remediation liabilities, and transport infrastructure constraints.
4. 4Day 10-12: Practice 9-mark essay outlines evaluating the balance between technological advancements and geological limitations.

• 📋Quantitative data analysis: calculating cut-off grades, ore recovery percentages, or stripping ratios from geological borehole tables.
• 📋Structured explanatory questions: detailing how high water tables or complex mineral chemistries raise operational processing costs.
• 📋Synoptic evaluation essays: assessing how changing world commodity prices or stricter environmental policies alter reserve boundaries over time.