Exercises: Geological resources: exploitation and responsible use

State four minerals or rocks in everyday use (for example, gypsum, salt, quartz, or limestone), indicate one application for each, and explain what type of deposit or quarrying/mining operation they are obtained from.

Define ore and gangue in a metallic deposit and explain what determines whether a deposit is profitable to mine, considering the metal price and the proportion of ore.

Reason why geological resources are considered non-renewable on a human scale and what two strategies make it possible to extend their availability — recycling and substitution with other materials —, providing an example of each.

Describe two environmental impacts of open-cast mining (on the landscape, water, or atmosphere) and explain what the subsequent restoration of a site consists of, citing a specific land recovery measure.

Lithium, cobalt, and rare earths are considered strategic resources. Explain for which technologies they are essential, what external dependency problem they pose for Europe, and what alternatives are being explored.

Observe the numbered mineral samples in the image. a) Identify each one by its appearance (luster, color, crystal shape). b) State an everyday or industrial use for each mineral. c) Point out which ones are non-metallic and explain the difference between a metallic and a non-metallic mineral resource.

A mining company submits a project to reopen an open-pit polymetallic sulfide (copper and zinc) mine 3 km from the boundary of a Natural Park located on a karst massif with protected aquifers. The company defends its environmental viability by claiming that the pit is situated at a topographic elevation 80 m lower than the park's springs and that it will create 350 direct jobs in a demographically declining region.

1. a) Refute the company's hydrogeological argument: justify why the topographic difference does not guarantee hydrogeological safety in karst terrain if continuous dewatering in the pit alters the regional water table.
2. b) Predict the hydrochemical and hydrodynamic consequences for the Natural Park's springs of forming a cone of depression that reverses the hydraulic gradient.
3. c) As an environmental officer, design three non-negotiable technical conditions (related to piezometric monitoring, tailings confinement, and the post-closure restoration bond) that you would demand in order not to issue an unfavorable Environmental Impact Statement.

"Urban mining" recovers metals from electronic waste. Explain what it consists of, why the proportion of valuable metal in a cell phone exceeds that of many natural ores, and what technical and social obstacles are hindering its take-off.

Analyse the following simplified Life Cycle Assessment (LCA) data for the production of 1 t of aluminum:

• Primary aluminum (from bauxite): energy consumption = 170 GJ; emissions = 12 t CO₂ eq; solid waste = 1.8 t of caustic red mud containing heavy metals.

• Secondary aluminum (scrap recycling): energy consumption = 15 GJ; emissions = 0.6 t CO₂ eq; solid waste = 0.1 t of salt slag.

1. a) Interpret the data and calculate the percentage of energy savings and GHG emission reductions achieved by the circular economy for this metal compared to the linear extractive route.
2. b) In the automotive industry, different aluminum alloys are blended with magnesium, zinc, or silicon. Justify why "downcycling" (recycling with a loss of purity and mechanical properties) poses a bottleneck to closing the loop and how ecodesign can prevent it.
3. c) A manufacturer claims: "Replacing aluminum with carbon-fiber-reinforced polymers in vehicles reduces the overall ecological footprint because it avoids bauxite mining." Refute or qualify this statement by analysing the full life cycle of the substitute (petrochemical origin and difficulty of end-of-life recycling).