Exercises: Resources, mineral deposits and reserves

Define natural resource and classify the following as renewable or non-renewable: groundwater, copper, wind, agricultural soil, and oil. Justify any borderline cases.

The diagram shows the total known resources of a mineral (blue rectangle) and the portion that currently constitutes the reserve (green rectangle). Explain the difference between resource and reserve and reason what economic or technological change could be represented by the arrow marked '?', which expands the reserve without discovering new deposits.

What conditions must a mineral concentration meet to be considered a mineral deposit? Explain the role of ore grade and market price.

Compare open-pit mining and underground mining: which geometric factor of the deposit (depth and shape) decides the choice of each method?

What is a critical or strategic mineral resource? Name two examples and explain what makes them critical (technological importance and supply risk).

What is the stripping ratio in an open-pit mine and how does it influence its profitability?

What are the ore and the gangue of a deposit? What happens to the gangue during ore processing?

Choose three geological materials present in your daily life (cell phone, housing, food) and trace the origin of each back to the mineral, rock, or deposit from which it comes.

Silica sand for glassmaking is an abundant resource, whereas tantalum is scarce and strategic. Compare how geological abundance and technological concentration influence the price and geopolitics of both resources.

Deposits are concentrated in a few countries for strictly geological reasons. Explain this concentration and analyze two geopolitical consequences (supply dependence, price fluctuation).

Describe the phases of the life of a mine (prospecting, exploration, exploitation, closure and restoration) and state what is decided in each one.

A life cycle assessment compares the replacement of 100 000 diesel vehicles with 100% electric vehicles equipped with lithium-nickel-manganese-cobalt (NMC) batteries. The study concludes that, while greenhouse gas emissions are reduced by 65% over the vehicle's lifespan, cumulative environmental toxicity and water consumption increase by 280% in the source extraction regions (lithium salt flats and the cobalt belt).

1. a) Explain the environmental paradox of "clean technologies" relying on the concept of the externalization of environmental impacts throughout the mineral raw material supply chain.
2. b) Design a technical proposal with two viable alternatives (for example, using cobalt-free cathode chemistries such as LFP or sodium, or direct lithium extraction technologies with brine reinjection) and justify how they would mitigate the identified hydrological and geochemical impacts without compromising the decarbonization of transport.

At the beginning of the 20th century, copper mining exploited deposits with average grades exceeding 3 % (30 kg of useful Cu per metric ton of extracted ore). Today, large global porphyry copper deposits extract ore with grades around 0.5 % (5 kg of Cu/t). At the same time, electrification is driving up consumption: a conventional electric vehicle requires 80 kg of copper (compared to 20 kg in an internal combustion engine vehicle) and a wind farm requires about 4 metric tons of Cu for each megawatt (MW) installed.

1. a) To manufacture a fleet of 20 000 electric vehicles from a deposit with a grade of 0.5 %, a metallurgical recovery of 80 %, and a waste-to-ore ratio of 2:1, calculate the mass of ore that must be processed and the mass of waste rock that must be removed. From the results, deduce and explain three serious geo-environmental impacts resulting from such a scale of material removal.
2. b) An industry representative states that "recycling e-waste (waste electrical and electronic equipment, or WEEE) will make it possible to dispense with primary copper mining in the next 15 years." Substantively refute this claim considering the demand growth rate, the time lags due to equipment service life, and the thermodynamic limitations of recycling.

A mining company is applying for environmental authorization to exploit a lithium pegmatite deposit via an open pit 160 m deep. The planned operation is located 1.5 km upstream of a karst aquifer that feeds springs providing drinking water to two towns and supporting traditional irrigated agriculture. The project report includes intensive pumping to dewater the open-pit water table, acid leaching ponds, and an external waste dump that will accumulate waste rock containing arsenopyrite and pyrite.

1. a) Predict the two most serious hydrogeological and geochemical risks to the karst aquifer and surface waters, explaining in detail the chemical reactions that trigger acid mine drainage and the release of toxic metalloids such as arsenic.
2. b) Design three specific, measurable, and essential technical conditions that the Environmental Impact Statement (EIS) should impose to authorize the project (consider waste dump sealing, piezometric monitoring, and effluent treatment).
3. c) Justify whether changing the extraction method to underground mining using the underhand cut-and-fill technique with inertized waste rock pastes would significantly reduce impacts on the landscape, the water balance, and leachate generation compared to the open pit.