Exercises: Uses of rocks and minerals

Look at the diagram: on the left there are five numbered everyday objects and on the right, five minerals in random order. Match each number with the letter of the mineral from which the object originates, and explain, in two of the cases, which property of the mineral makes it useful for that purpose.

State three different uses of rocks in buildings in your local area (facades, pavements, roofs, monuments, etc.) and name the rock used in each case if you know it.

Gypsum, common salt (halite), and quartz are minerals with very different uses. Name an everyday use for each one and explain which property of the mineral makes it useful for that purpose.

Name two metals obtained from minerals extracted from the Earth's crust and one everyday use of each.

What is clay used for? Name two products from your daily life made with it and explain what happens to clay when it is fired in a kiln.

Name two rocks used in construction and explain in which part of a building each one is used.

Besides cooking, name two uses of common salt (halite) and explain which property of salt makes them possible.

Explain what a quarry is and how it differs from a mine, giving an example of a material obtained in each one.

For a kitchen worktop, there is a choice between granite and marble. Take into account that marble is metamorphosed limestone that reacts with acids (lemon, vinegar), whereas granite is very hard and hardly alters. Recommend an option and justify your choice.

Rocks and minerals are non-renewable resources. Explain what this means, give two examples of materials whose reserves are decreasing, and suggest two measures to consume them more sustainably.

An open-cast quarry provides employment for a town, but destroys a hillside and generates dust and noise. Set out two arguments in favour of and two arguments against the quarry, and conclude by giving your reasoned opinion.

Copper is used in electrical cables and iron in building beams. Relate each use to the property of the metal that makes it possible and name a material that could replace each one, reasoning whether it would perform the same function.

Mobile phone and electric car batteries need lithium and cobalt. Explain why the demand for these minerals is growing and raise one problem that so much extraction can create.

To obtain one tonne of copper, many tonnes of rock must be extracted and processed. Explain why mining generates mountains of waste (spoil heaps) and what problems these accumulations can cause to the landscape and to water.

Window and bottle glass is made from sand very rich in quartz. Explain which process turns sand into glass and discuss why crushed recycled glass is added to the mixture: what is saved by doing so.

In prehistory, obsidian and flint were used to make arrowheads and knives. Explain which property of these rocks made them so useful and which materials gradually replaced them over time.

A technology manufacturer claims in its advertising campaign: «Our new smartphone is 100% eco-friendly because its battery lasts twice as long and the casing is made of polished aluminum instead of plastic». Knowing that batteries require lithium and cobalt from mining operations, and that aluminum is extracted from the mineral bauxite through highly energy-consuming processes:

1. a) Refute the company's claim by justifying why no electronic device can be considered «100% eco-friendly» given the geological origin of its raw materials.
2. b) If doubling the battery life requires doubling the amount of lithium and cobalt per device, predict two environmental or social impacts in the countries where these mines are located if sales increase by 20%.
3. c) From the perspective of responsible consumption of mineral resources, justify whether it is more sustainable to change phones every two years to have a more efficient battery or to prolong the use of the same phone for four years by only replacing the deteriorated battery.

In a historic municipality, three heritage elements are going to be restored, and suitable local rocks must be selected: the load-bearing pillars of a river bridge, the flat roof tiles of the town hall, and the carved sculpture on the facade of a church.

1. a) Justify which traditional rock (granite, slate, or easily carved limestone) you would choose for each of the three works, relating your choice to a specific geological property of each rock (impermeability and sheet foliation, hardness and mechanical strength, or ease of carving).
2. b) To obtain the necessary limestone, there are plans to reopen an old open-pit quarry near the town, which triggers protests due to its visual impact and dust. Design three corrective measures that the operating company should implement to minimize the footprint on the landscape and restore the relief at the end of the extraction.

An information brochure makes a mistake by stating: "Recycling aluminium cans barely saves energy, because melting the used metal requires ovens at extremely high temperatures, just like extracting it from the ore."

Actual data:

• Producing 1 kg of primary aluminium from bauxite ore requires crushing, chemical refining, and high-temperature electrolysis, consuming 200 MJ.

• Recycling 1 kg of aluminium from used cans only requires melting it at 660 °C, consuming 10 MJ.

1. a) Numerically demonstrate the brochure's error by calculating the exact percentage of energy saved by recycling and how much energy would be saved in total if a school collects and recycles 50 kg of aluminium cans.
2. b) Bauxite is mainly extracted in rainforests and tropical areas through open-pit mining. Justify how aluminium recycling directly contributes to preventing deforestation and the loss of fertile soil in those regions of the planet.

During a debate on natural resources, a student states: "In our classroom, almost everything is synthetic or artificial: the glass windows, the plaster and brick walls, the copper cables for the projector, and the steel shelves. Therefore, today's society no longer depends on the extraction of rocks and minerals from the ground."

1. a) Refute their argument by completing a geological analysis of these four items: identify the rock or mineral of origin for each one (quartz or silica sand, gypsum rock, clay, metallic mineral such as chalcopyrite or hematite) and briefly describe the necessary transformation.
2. b) Classify the geological resources mentioned into: metallic minerals, non-metallic minerals, and industrial rocks.
3. c) Predict what consequences the depletion of aggregates (sand and gravel) and limestone rocks would have on the construction of housing and infrastructure, justifying their role in the manufacture of concrete and cement.

An open-pit mining operation extracts 500 tonnes of rock daily with an ore grade of 5 % in copper (the exploited mineral is chalcopyrite, which is mixed with abundant pyrite and quartz, forming the gangue).

1. a) Calculate how many tonnes of pure copper are obtained each day and how many tonnes of waste rock (debris without economic value) are generated in a single day.
2. b) When the pyrite (iron sulfide) in the waste rock is exposed to air and rainwater, a chemical reaction is triggered that acidifies the water and dissolves heavy metals (a phenomenon known as acid mine drainage). Predict what will happen in the nearby river and aquifer if the company accumulates this waste rock on an unsealed slope.
3. c) Compare these two management options: depositing the waste in a large surface tailings pond, or using it to backfill depleted mine voids by mixing it with neutralizing materials. Justify which of the two options poses a lower long-term geological risk.

A mining basin closes its last coal (anthracite) mine. The resulting landscape features a large open-pit cut (a huge artificial crater), large unstable spoil heaps devoid of vegetation, and black sediment issues in the streams.

1. a) Justify the closure of the operation from the perspective of the carbon cycle and the climate crisis, explaining what geological process formed coal in the past and what environmental consequences its combustion had in thermal power plants.
2. b) Design a technical proposal to stabilize the spoil heaps and prevent the geological risk of landslides and water erosion during torrential rains.
3. c) The town council is debating between two redevelopment projects: filling the open pit with water to create a recreational lake and nature reserve, or installing a photovoltaic solar farm on the terraces of the old mine along with an interpretation centre for geological and mining heritage. Evaluate the pros and cons of each option and justify which one is more suitable for the environmental recovery of the area.

A large portion of the world's lithium is concentrated in the salt flats of the Atacama Desert in the form of underground brines. The extraction method consists of pumping this salty water into gigantic surface ponds so that solar heat evaporates the water and crystallises the lithium salt. To obtain one tonne of lithium, about two million litres of water must be evaporated.

1. a) Identify which physical method of mixture separation is used and explain why this mining extraction technique is only economically viable in climates with very specific meteorological characteristics.
2. b) Hydrogeological studies indicate that the water level of the basin's underground aquifers has dropped several metres in the last decade. Interpret this data and predict two impacts: one on the aquatic fauna of the salt lagoons (such as flamingos) and another on the traditional agriculture of local indigenous peoples.
3. c) In European cities, the use of lithium batteries is encouraged to reduce local air pollution. Critically justify the environmental dilemma of solving urban pollution at the cost of intensifying water stress in distant arid ecosystems.

Analyse the following comparative data between obtaining copper and gold in conventional rock mines versus through "urban mining" (recycling printed circuit boards from discarded computers and mobile phones):

• Rock deposit: From 1 tonne of rock, between 1 and 5 grams of gold and about 8 kg of copper are extracted. 99 % of the extracted rock ends up in spoil heaps as waste.

• Urban mining: From 1 tonne of electronic boards, about 250 grams of gold and more than 120 kg of copper are obtained, with an energy expenditure up to 80 % lower.

1. a) From the data, calculate how many tonnes of mineralised rock would have to be blasted and processed in a natural mine (with an average ore grade of 2,5 grams of gold per tonne) to obtain the same amount of gold contained in a single tonne of electronic boards.
2. b) Justify, considering the alteration of the relief, the destruction of soil, and the volume of geological waste, why urban mining causes a drastically lower landscape impact than open-pit mining.
3. c) A manufacturer states: "If we recycle all old devices, there will no longer be any need to extract more minerals from the Earth's crust." Refute this statement by providing two technical or socioeconomic reasons showing why recycling alone cannot completely stop extractive mining activity.

Unit challenge. Have you ever thought about how much geology is hidden in the walls of your home or your everyday objects? You are going to prepare a "Domestic Geological Audit Report" to find out.

1. Geological inventory: Select $4$ everyday objects from your home made of rocks or minerals (for example: tiles, countertop, pencil graphite, copper cables, or table salt). Identify which rock or mineral they contain, describe two observable physical properties (hardness, lustre, cleavage, or colour), and classify each rock according to its origin in the rock cycle (igneous, sedimentary, or metamorphic); if it is a mineral or a metal obtained from one, state in which type of rock or environment its raw material forms.

2. Source tracing: Access the official website of the IGME (Instituto Geológico y Minero de España) or the INE to check whether any of these raw materials are extracted in your autonomous community, and note what type of deposit or quarry is required.

3. Proposal and sustainable cycle: Design a comparative table with your findings and write three reasoned measures to extend the lifespan of or recycle these items, explaining how their extraction influences the natural cycle of the lithosphere.

Assessment criteria:

• Correct identification of minerals, rocks, and their position in the lithological cycle.

• Rigor in describing physical properties and using data from official sources.

• Coherence and creativity in proposals for sustainability and responsible consumption.