The Lithosphere

Question 1

Three examples of metals and their uses.

Answer 1

Iron - buildings (reinforced concrete), transport (ships, road vehicles), fridges, washing machines.
Aluminium - packaging foil, vehicles window frames.
Copper - electric cables, water pipes.

Question 2

Three examples of industrial/construction materials and their uses.

Answer 2

Aggregates (sand and gravel) - concrete, building mortar, glass.
Limestone - Cement, crushed for road surfacing, building blocks.
Salt - deicing roads, food additive, source of chlorine for manufacture of paper, plastic, etc.

Question 3

What are igneous processes?

Answer 3

Where rocks and minerals are created by the cooling and hardening of magma and molten lava.

Question 4

Hydrothermal deposition is an example of an igneous process. What is it?

Answer 4

Igneous intrusions are rocks formed from magma that cools and solidifies within the Earth’s crust. The intrusions produce high temps that dissolves many minerals from surrounding rocks. These mineral-rich solutions travel along fissures away from igneous batholith, cooling as they do so. As they cool, dissolved minerals crystallise and come out of solution - happens in order of solubility, least soluble crystallising first.
This process of fractional crystallisation starts with a mixture of minerals that could not have been exploited. Once the minerals became separated and deposited, soon after the batholith formed, later exploitation became possible.

Question 5

What are some metal ores that are deposited by hydrothermal processes?

Answer 5

Tin, copper, lead, silver, gold and arsenic.

Question 6

What are metamorphic processes?

Answer 6

Igneous processes and tectonic movements of crustal plates can alter existing rocks with high temperatures and pressures, without melting them producing metamorphic rocks.
High temperatures and extreme pressure can change limestone to marble.
Extreme pressure can change mudstone into slate.

Question 7

What are sedimentary processes?

Answer 7

They cause minerals to settle and build up to produce layers deposited between sediment. This deposition and subsequent cement action at the Earth’s surface and within bodies of water creates sedimentary rocks and minerals.

Question 8

What are Proterozoic marine sediments?

Answer 8

These include iron ore deposits such as hematite and magnetite. They were formed when dissolved iron compounds became oxidised by the oxygen released by photosynthesis, producing insoluble iron oxide deposits.
This occurred mainly between 2.5 and 1.8 billion years ago.

Question 9

What are alluvial deposits?

Answer 9

Alluvial processes involve materials that were carried and separated by flowing water. The ability of water to carry solids depends upon the velocity of the water and the density of the solids. Materials that are exploited from alluvial deposits include gold, diamonds, tin ore, gravel, sand and clay.

Question 10

What are evaporites?

Answer 10

If a bay of an ancient sea became isolated, then the water may have evaporated, leaving crystallised minerals (evaporites) such as halite (sodium chloride).
Evaporites also form in inland seas in desert areas as the water from inflowing rivers evaporated.

Question 11

What is secondary enrichment?

Answer 11

Many economically important metals can from minerals that are soluble or insoluble depending on the conditions, especially the availability of oxygen. They may be transported in solution, by moving water, and then deposited as their oxidation state changes.

Question 12

What are biological sediments?

Answer 12

Biological processes are those where living organisms form mineral deposits. These processes often concentrate minerals that can be deposited in sedimentary rocks.

Question 13

What is Lasky’s Principle?

Answer 13

It states that: in general, as the purity of a mineral decreases, the amount of the mineral present increases exponentially.
So, the major problem with future mineral supplies is not the quantity that exists but the need to develop methods to exploit low-grade deposits.
To help with estimates of future availability, it is important to predict which deposits are likely to become exploitable in the future and when.

Question 14

What is a stock?

Answer 14

It includes all of the material that exists in the lithosphere.
It includes all of the mineral that can be exploited now, that will be exploited when prices rise, or new technologies are available, and that will never be exploited (economically or technologically).

Question 15

What is a resource?

Answer 15

It includes all of the material that is theoretically available for exploitation. This includes deposits that can be exploited plus those that cannot be exploited now, but with realistic increases in prices, or improvement in technologies, could be extracted in the future.

Question 16

What is a reserve?

Answer 16

They are defined as the amount of resource that can be exploited now, economically, using existing technology.

Question 17

What is IR spectrometry?

Answer 17

Different minerals emit infrared radiation at different wavelengths and these can be used to identify them.

Question 18

What is gravimetry?

Answer 18

Gravimeters detect variations in gravity caused by variations in density and mass. Igneous rocks are usually more dense than sedimentary deposits.

Question 19

What is magnetometry?

Answer 19

Magnetometers detect rocks that are more magnetic such as the iron ore magnetite and ores of tungsten and cobalt.

Question 20

What are seismic surveys?

Answer 20

These involve sound waves produced by controlled explosions, or a seismic vibrator on the surface. The echoes can give information about the death, density, and shape of rock strata.

Question 21

What is resistivity?

Answer 21

It is the measurement of the difficulty with which electricity passes through a material. In general, sedimentary rocks have lower resistivities than igneous rocks because they have higher water content.

Question 22

What is trial drilling?

Answer 22

The most expensive technique per sampling site but it is the only method that actually produces samples of the rocks underground.

Question 23

What is chemical analysis?

Answer 23

Laboratory tests confirm the chemical composition and purity of the minerals in the rock samples.

Question 24

How does ore purity affect mine viability?

Answer 24

The purity of an ore affects the financial costs of exploitation and the environmental impacts of mining.
If the ore grade is low, then more rock will have to be mined, more waste materials will be produced, more energy will be needed for mining and processing, and more pollution will be generated.

Question 25

How does chemical form affect mine viability?

Answer 25

The chemical form of the mineral ore affects the ease of chemical extraction of the metal. For example, aluminium can be extracted from bauxite (aluminium oxide) but not from clay (alumino-silicates) which is much more abundant.

Question 26

How does overburden and hydrology affect mine viability?

Answer 26

The overburden is the rock that lies above a mineral deposit. Hard overburden may require blasting which increases costs. Loose overburden ,at increases the risk of landslides, so the slides of the mine void may gave to be landscaped at a more gentle gradient. This may increase the overall area of the mine. Higher precipitation or impermeable rocks below may increases drainage costs.

Question 27

How does the depth affect mine viability?

Answer 27

Costs rise rapidly as the depth increases. If the depth is doubled, the the cost more than doubles. The sides of the mine cannot be vertical because if the risk of collapse. So the amount of rock that must be removed reach the mineral rises rapidly as depth increases. As depth increases, the amount of water that flows into the mine from surface runoff or groundwater also rises, increasing pumping costs significantly.

Question 28

How does the cut-off ore grade affect mine viability?

Answer 28

Mining has to be an economically profitable activity, so there must be a balance between production costs and income. The lowest ore purity that can be mined economically, using existing technology, is called the cut-off ore grade. The COOG changes as technology improves and market prices fluctuate.
Mineral reserves include deposits that are above the COOG.

Question 29

How do transport costs affect mine viability?

Answer 29

Transport costs are affected by the distance to market, the ease of bulk transport, the presence of a suitable existing transport infrastructure and whether the bulk of the mineral has been reduced by processing.

Question 30

How has mineral exploitation affected land take?

Answer 30

Minerals can only be exploited where they were deposited, which makes land use conflicts more likely, as there is a limited choice of locations that can be exploited.
Land is required for associated buildings, access routes, and possibly a buffer zone between the mine and neighbouring areas. Open cast mining causes much more habitat loss than deep mining, but the land area that is required to access the mineral is larger than the mine void itself.

Question 31

How has mineral exploitation caused habitat loss?

Answer 31

The loss of species where the mineral is being extracted is unavoidable as the surface habitat must be removed. Removing wildlife by capturing animals and transplanting plants to other areas has been attempted but is rarely completely successful, especially with species that are difficult to find/capture.
Mining can have serious impacts on the environment, but these can often be minimised by good min management and are localised.

Question 32

How has mineral exploitation caused the loss of amenity?

Answer 32

Mining changes the landscape and can create aesthetic problems for local communities. These effects may be reduced by landscaping and tree planting. When the mine closes it can be turned into a community resource so the long term amenity value may be greater than that of the area before mining took place.

Question 33

How has mineral exploitation affected noise?

Answer 33

Mine vehicles and rock blasting are the two main sources of noise. Embankments or ‘baffle mounts’ can be built around the mine to help absorb and deflect the noise.
Blasting in mines does not usually take place day and night, but it can be disturbing to the locals, especially if it unexpected. It can be mitigated, though, by blasting at set times of day so the noise is predictable.

Question 34

How has mineral exploitation affected turbid drainage water?

Answer 34

Suspended soil particles in mine drainage water can reduce light penetration into rivers and lakes. Sediments can also cover and kill plants and animals.
The turbidity of drainage water can be reduced by using sedimentation lagoons in which the water stands still for long enough for the solid to sink, so the outflow water has low turbidity.

Question 35

How has mineral exploitation affected spoil disposal?

Answer 35

Spoil is the solid waste material left behind by mining. It can include overburden material, unwanted material extracted with the mined mineral, and solid wastes from the chemical processing of the mineral. Spoil needs to be disposed of carefully, as it can cause a variety of problems:
1. Aesthetics - spoil heaps can damage the scenic beauty of an area (landscaping the spoil heap can make it look more natural).
2. Stability - a lack of surface compaction can reduce surface stability and lead to erosion (can be reduced by landscaping to reduce gradients).
3. Leachate - rainwater percolating through spoil can dissolve toxic metals and sulphides that produce acidic leachate solutions.

Question 36

How has mineral exploitation lead to mine site restoration?

Answer 36

New uses may be found for sites that have previously been used for mining and mineral processing.
The use of the site after mining will depend upon its location, access, topography and any residual problems such as spoil heaps containing toxic wastes.

Question 37

How will better remote sensing image resolution help with future mineral supplies?

Answer 37

Newer satellites may carry improved sensors which generate greater numbers of image pixels.
Multispectral sensors detect a greater range of wavelengths of visible and infrared light, providing more detailed information on the mineral composition of the Earth’s surface.

Question 38

How will portable field equipment help with future mineral supplies?

Answer 38

Laboratory equipment has become smaller and more portable as electronic components have become lighter, more powerful batteries have been developed and energy consumption has been reduced.
Portable equipment is available for infrared spectroscopy, X-ray fluorescence, and radiation detection. These save time as results are available immediately and it is no longer necessary to wait for laboratory results to be received.

Question 39

How have improvements in mechanisation helped future mineral supplies?

Answer 39

1. Deep mining - Using machines allows mining underground where it may be too hot or dangerous for people, e.g., deep gold and platinum mines in South Africa, at depths up to 3.8km.
2. Open-cast mining - Larger machinery in open-cast mines allows overburden and minerals to be extracted more quickly and cost-effectively. Using machinery that weighs over 13000t allows deeper open-cast mines to be developed with mines over 600m in depth being possible for more valuable minerals.

Question 40

How have improvements in the exploitation of low grade deposits helped future mineral supplies?

Answer 40

Smelting is the normal method to extract a metal from its ore. It involves chemical reduction at high temperatures. The amount of energy needed increases rapidly as the ore purity declines, so economically viable exploitation may only be possible if new methods can be developed.

Question 41

What is bioleaching?
(in terms of low grade deposit exploitation)

Answer 41

The use of living organisms to extract metals from their ores. The metals in the solution produced by bioleaching can be separated by electrolysis, or by using carbon filters.

Question 42

What is phytomining?
(in terms of low grade deposit exploitation)

Answer 42

Some plants absorb metal ions from soil or water and concentrate them in their leaves. This can be used as a method of decontaminating polluted sites and as a method of commercial extraction of metals. Once the plants have absorbed the metals, the vegetation is harvested and incinerated. The concentrated metals in the ash can be dissolved using acids, then separated by electrolysis.

Question 43

What is iron displacement?
(in terms of low grade deposit exploitation)

Answer 43

Iron is a more reactive metal than copper and will displace copper ions from solution. The solid iron goes into solution as the copper ions are deposited as solid copper metal which can be collected.

Question 44

What is leachate collection?
(in terms of low grade deposit exploitation)

Answer 44

Rainwater percolating through spoil heaps dissolves soluble metal ions. The draining leachate can be recirculated through the spoil heaps to increase the concentration of metal ions in solution. When the concentration is high enough, the metals can be extracted from the solution by electrolysis.

Question 45

What are rare earth metals?
(in terms of low grade deposit exploitation)

Answer 45

They are used in small amounts in many important applications, especially electrical, and electronic appliances. Exploitable deposits on land are limited and are mainly found in China. Chemical separation is complication and produces large amounts of toxic wastes.
Therefore, new techniques are being developed, such as bacterial adsorption, where dissolved ions of the rare earth metals become more concentrated as the absorb onto the cell surfaces of bacteria such as Bacillus subtilis. The metals can be separated by washing them off the bacteria using acidic solutions, with different metals being washed off at specific pHs.

Question 46

What is polymer adsorption?
(in terms of low grade deposit exploitation)

Answer 46

Metal ions dissolver in seawater will adsorb onto the surface of some polymers and can be collected later. Synthetic polymers can be used, as can natural polymers such as lignin from wood and chitin from discarded shrimp shells. This method is being developed to extract uranium and may provide a low-energy method of producing fuel for the nuclear power industry.

Question 47

How have polymetallic nodules helped in exploiting previously inaccessible deposits?

Answer 47

They are also called manganese nodules.
They are metal-rich nodules found on the seabed of many of the Earth’s oceans. Most of them are 5-10cm in diameter and are found at depths of 4000-5000m.
Large scale exploitation will be expensive and will require international agreement on the ownership of the seabed and its resources.

Question 48

What are the environmental impacts of polymetallic nodules?

Answer 48

Recovering nodules will disturb the seabed and kill benthic organisms that live there.
Separating the nodules from the seabed sediments would increase the turbidity of the water with unknown consequences. Re-disposition of the sediments is likely to kill filter feeders, also covering and killing benthic organisms.

Question 49

How has recycling helped future mineral deposits?

Answer 49

Manufacturing industry usually makes new products from freshly extracted raw materials but used materials can also be reused. The wastes may come from two sources:
1. Pre-consumer wastes - e.g., the waste trimmings produced by cutting or stamping machines.
2. Post-consumer wastes - such as discarded consumer products.
Most materials in domestic waste can be recycled if they’re separated

Question 50

How has recycling helped future mineral deposits?

Answer 50

Manufacturing industry usually makes new products from freshly extracted raw materials but used materials can also be reused. The wastes may come from two sources:
1. Pre-consumer wastes - e.g., the waste trimmings produced by cutting or stamping machines.
2. Post-consumer wastes - such as discarded consumer products.
Most materials in domestic waste can be recycled if they’re separated, which is the most effective way when undertaken by the public before waste collection, as it prevents reduction in quality caused by mixing of wastes, e.g., paper and food waste.

Question 51

Why can transport be a problem with recycling schemes?

Answer 51

Extraction of aluminium ore involves bulk resources where bulk transport can be used creating major economies of scale and lower unit cost. Recycling may involved the collection and transportation of smaller quantities of materials which is more expensive and bulk transport is not possible. However, recycled materials will be lighter than the original raw materials.

Question 52

Why can labour costs be a problem with recycling schemes?

Answer 52

Processing smaller quantities of materials increases labour costs. However, recycling work does not usually require he level of skills or training that extraction requires, so labour costs will be lower.

Question 53

Why can separation be a problem with recycling schemes?

Answer 53

Alloys of mixed metals cannot easily be separated. So, recycled aluminium alloys cannot be used where pure aluminium is needed.

Question 54

Why can identification be a problem with recycling schemes?

Answer 54

It is labour intensive and slow work to identify the composition of recycled materials where the composition is important for reuse.

Question 55

Why can energy costs be a problem with recycling schemes?

Answer 55

Recycling aluminium saves the energy needed for extraction of aluminium from bauxite. However, this saving may be exceeded by the energy used for transport if only small quantities are collected.

Question 56

Why can public cooperation be a problem with recycling schemes?

Answer 56

Successful post-consumer recycling schemes require public cooperation to separate waste. If the public do not cooperate. the scheme will not be successful.

Question 57

Why can waste losses be a problem with recycling schemes?

Answer 57

Not all used materials can be recycled. Some are unavoidably lost where litter is discarded or placed in general waste for landfill.