Resources, deposits and reserves

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

Choose three geological materials present in your daily life (mobile 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.

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.

What is the grade of an ore and in which units is it expressed for a common metal and for a precious metal? Give a numerical example of each case.

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

A copper ore with a grade of $0,8\ \%$ is viable to extract in an open-pit mine, whereas one with a grade of $0,1\ \%$ would not be. Explain what cut-off grade is and on what factors its value depends.

A mine exploits $2\ \text{Mt}$ of ore with a grade of $0,5\ \%$ copper.

1. a) Calculate the tonnes of copper contained in the ore;
2. b) explain why the metal actually obtained will be less (metallurgical recovery).

A sphalerite (ZnS) mining operation works a deposit with an average grade of 4,5% Zn. Direct extraction and processing costs amount to €90 per ton of treated ore, with a metallurgical recovery of 80%.

1. a) If the market price of zinc drops on the stock exchange from €3000/t to €2000/t of metal, demonstrate numerically why the operation incurs losses and is forced to halt its activity, justifying how the deposit is reclassified in the McKelvey diagram (from reserve to subeconomic identified resource).
2. b) Ten years later, with the price of zinc remaining at €2000/t and without discovering new ore, the mine reopens profitably thanks to the introduction of bioleaching and selective crushing, which reduce costs to €65/t of ore and raise recovery to 85%. Numerically justify the new viability and draw a conclusion about the dynamic and relative nature of the concept of reserve compared to that of geological resource.

A mining company is exploring a granitic massif in search of tungsten (scheelite). In a preliminary phase, using scarce boreholes spaced 1 km apart, it estimates an overall volume of 30 million tonnes of rock with an assumed grade of 0,15 % WO₃. The economic cut-off grade of the operation is currently at 0,28 % WO₃.

1. a) Place this deposit on both axes of the McKelvey diagram (geological certainty and economic feasibility), justifying why it should be classified as a resource and not as a reserve.
2. b) Following a close-spaced drilling campaign (50 × 50 m) with continuous coring and geochemical analysis, a block of 8 million tonnes with an average grade of 0,40 % WO₃ is delineated, while the remainder of the volume stays at 0,12 %. Explain with reasons how each of the two fractions is reclassified in that diagram.
3. c) If the regional administration approves an environmental land-use tax and demands an environmental restoration bond that raises the mine's cut-off grade to 0,42 % WO₃, predict and justify the immediate impact of this regulation on the amount of commercially exploitable reserves held by the company.

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

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

Deposits are classified by their genesis into magmatic, hydrothermal, sedimentary (placers) and metamorphic. Briefly describe each process and give an example of a substance extracted from each type.

Deposits are concentrated in a few countries for strictly geological reasons. Explain this concentration and analyse 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.

What does mineral exploration consist of? Order the usual techniques (geological mapping, soil geochemistry, geophysics, drilling) from lowest to highest cost and state what each one provides.

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

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.

In the 1970s, geophysicist M. King Hubbert and his followers predicted, by applying a symmetrical logistic curve to known conventional oil reserves, that global production would reach an insurmountable peak around the year 2000 and then enter a rapid decline. However, in 2023 global production exceeded 100 million barrels per day.

1. a) Critically analyse which geological and socioeconomic assumptions of Hubbert's model proved insufficient to anticipate the boom in unconventional oil (shales and tar sands via hydraulic fracturing) and enhanced oil recovery (EOR) techniques.
2. b) Drawing on the concept of Energy Return on Investment (EROI), refute the claim that "continuous technological advancement guarantees that an extraction peak limiting the net availability of fossil energy for society will never exist."

Two developing countries, A and B, simultaneously discover large natural gas and coltan deposits. Thirty years later, Country A suffers the consequences of the "Dutch disease": its currency appreciated, cheap imports ruined its local agriculture and industry, corruption captured the extractive revenues, and the recent international drop in gas prices has plunged the State into a severe debt crisis. In contrast, Country B has achieved a diversified economy, high human development indices, and manages a sovereign stabilization fund.

1. a) Explain the cause-and-effect sequence that connects the massive discovery of geological resources with the decline of the other economic sectors in Country A, defining precisely the mechanism of the Dutch disease.
2. b) Contrast the governance factors that make the difference between both countries and reason why dependence on non-renewable mineral resources with volatile prices is particularly destabilizing for public finances.
3. c) Design three strategic public management and fiscal guidelines for Country A to reverse its situation and transform exhaustible natural capital into lasting and sustainable productive capital.

Neodymium and cerium have an average abundance in the Earth's crust (38 ppm and 60 ppm, respectively) notably higher than that of traditional metals such as lead (13 ppm) or silver (0,07 ppm). However, the European Union classifies them as critical raw materials with an extreme geopolitical supply risk, depending on a single country for more than 90 % of both mineral concentrate and chemical refining.

1. a) Justify, from the perspective of geochemical behaviour and the crystal structure of minerals, why these elements rarely form concentrated ores and require hydrometallurgical separation and refining processes that are extraordinarily complex and environmentally aggressive.
2. b) Minerals such as monazite and bastnäsite often host significant concentrations of radioactive thorium and uranium. Evaluate the socio-environmental conflicts arising from opening rare earth mines in European territory versus the ethical dilemma of outsourcing pollution to countries with lax environmental regulations.
3. c) Assess the feasibility in the short and medium term of meeting the demand for neodymium for wind turbines and electric vehicles exclusively through "urban mining" (recycling of permanent magnets), justifying the thermodynamic and temporal limitations that exist.

At the beginning of the 20th century, copper mining exploited deposits with average grades exceeding 3 % (30 kg of useful Cu per tonne 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 tonnes 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 WEEE (waste electrical and electronic equipment) 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.