Rock and Minerals and their Exploitation

Page 1: ROCKS AND MINERALS AND THEIR EXPLOITATION CHAPTER-1

Page 4: CRUST

  • The crust is a solid layer of rock on the surface of the planet.

  • The thickness varies between 3 and 30 miles.

Page 6: Types of Rocks-Igneous, sedimentary and metamorphic rocks

  • Igneous rocks:

    • Made when liquid magma cools to form solid rock.

    • Molten rock below the surface is called magma, and lava when it reaches the surface.

    • Extrusive igneous rock: if the rock cools quickly, small crystals are formed e.g. basalt (iron and magnesium).

    • Intrusive igneous rock: if the rock cools slowly, large crystals are formed e.g. granite.

    • Examples: Granite and Basalt

Page 8: Sedimentary rocks

  • Formed by the weathering of existing rocks at the Earth’s surface.

  • Fossils may be present.

  • Sediments (small particles of rocks) accumulate into layers and get pressurized due to the newer deposits above them.

  • The sediments are transported by water and wind (erosion).

  • Particles like clays, silts, sands, gravels, and small boulders are found in sediments.

  • Examples: limestone, sandstone, and shale.

Page 10: Metamorphic rocks

  • Formed from the existing rock when heat and/or pressure causes changes in the rock crystals without melting it.

  • The changes can be physical, chemical, or both.

  • Sedimentary and igneous rocks can become metamorphic rocks, and a metamorphic rock can become another metamorphic rock.

  • Metamorphic rocks are usually harder than sedimentary rocks.

  • Examples: marble and slate.

Page 12: Igneous Sedimentary Metamorphic

  • Made from liquid magma

  • Made from other rock fragments

  • Made from magma

  • Magma cools to solid rock

  • Rock fragments become buried and increased pressure forms a rock

  • Mineral crystals present; the size of the crystals depends on the speed of cooling

  • No fossils present

Page 13: Weathering and erosion break off fragments of surface rock.

  • The eroded rock is transported to another location.

  • The fragments of rock are deposited and built up in layers.

  • As the layers build up, the lower layers are compacted into sedimentary rock.

  • Sedimentary and igneous rocks subjected to heat and pressure underground form metamorphic rocks.

  • At higher temperatures, rocks melt to form magma.

  • Magma cools to form igneous rock.

  • Movements in the Earth raise rocks to the surface via a process called uplift.

Page 15: Extraction of rocks and minerals from the earth

  • Exploring for minerals:

    • Prospecting: a process of searching for minerals by examining the surface of the rocks.

    • Ore: A rock with enough important mineral to make it worth mining.

Page 16: Methods of exploration

  • Remote sensing:

    • Photographs of the area are taken from the air.

    • The images are carefully analyzed for mineral presence.

    • Aerial photography can cover more ground than a person on the surface.

  • Satellite signals:

    • Some satellites send signals to the Earth’s surface and collect the reflected signals, indicating the presence of minerals.

    • The unique radiation pattern is processed and analyzed by computers.

    • The system works in all weather conditions.

    • The GPS gives the exact location.

    • Large area covered in low cost.

    • Most efficient method.

Page 22: Methods of extraction

  • Surface mining:

    • Open cast/Open pit/Open cut

    • Strip mining

  • Subsurface mining:

    • Deep mining

    • Shaft mining

Page 24: Surface mining- OPEN PIT MINING

  • Deposit near the surface under a worthless material (overburden) to be removed before mining and can be used for mining restoration.

  • Sections-benches.

  • Quarries.

  • Eventually stops→ valuable deposits all removed, overburden increased and unprofitable to remove.

Page 25: Strip mining

  • Seam (an underground layer of a mineral such as coal or gold) of mineral.

  • Bucket wheel excavator.

Page 26:

  • Subsurface mining involves making tunnels to reach deep mineral deposits.

    • Horizontal mines are drilled to reach coal seam inside a mountain, entered by adit.

    • A sloping tunnel is constructed to lower down the machine.

    • Waste and rocks can be taken out.

    • Vertical shafts are made and then horizontal galleries.

Page 27:

  • Disadvantages of subsurface mining:

    • Expensive and technically challenging.

    • Requires supply for fresh air and water drainage.

    • Dangers of collapsing tunnels.

    • Risk of poisonous gas.

    • Explosion.

    • Underground fire.

Page 28:

  • Underground mining methods:

    • Dragline removing mountain up the rock.

    • The doctor along contour bench coal beds.

    • Auger or thin-seam miter along the control bench.

    • Driftmine.

    • Dragline in area mine rockspod.

    • Slope mine coal beds.

    • Shaft mine.

Page 29:

  • Factors affecting the viability of extraction of minerals:

    • The cost of exploration and extraction.

    • Geology.

    • Climate.

    • Accessibility.

    • The environmental impact.

    • Supply and demand.

Page 30:

  • Greenfield sites are areas that have never been mined for minerals.

    • The chances of finding a deposit there are low.

    • The strike rate for some metal ores ranges from 1:50 to 1:100.

    • New gold deposits are hard to find, strike rate may be as low as 1:1000.

  • Brownfield sites are areas that have already been mined.

    • Usually have a higher strike rate than greenfield sites.

    • Even low-grade deposits that were not extracted in the past may have enough value to be mined for profit.

Page 31:

  • Factors affecting the viability of extraction of minerals:

    • Quality of the mineral deposit.

    • Size of the deposit.

    • Transportation methods.

      • Bulk carriers (large ships) to keep transport costs low.

      • Rail transport is also cost-effective.

      • Direct shipping ore with a long-term agreement with the government.

Page 32:

  • Changes in the world price of copper from 1989 to 2012.

Page 33:

  • Impact of rock and mineral extraction:

    • Environmental impacts:

      • Ecological impacts.

        • Loss of habitat.

        • Effect on the food chain (surface mining).

        • Deep mining results in less initial area, and wastes from mining stored above ground.

        • Solution: overburden can cover and create new vegetation.

      • Environmental impact assessment required.

        • Mining company should keep loss of land as small as possible and restore the land after mining.

    • Economic impacts:

      • Pollution.

        • Noise, water, land, air, and visual pollution.

        • Noise can disturb animal behavior and cause health problems for people.

        • Deep mining results in less noise than surface mining.

        • Mining licenses set limits on noise levels and working hours.

      • Water pollution.

        • Drinking water polluted.

        • Acidification of water, toxic heavy metals.

        • Biomagnification.

Page 35:

  • Mercury levels in the food chain.

  • Advice for consumption of different fish species.

Page 36:

  • Dust can reduce plant growth and be dangerous to human health.

  • Informal mining can lead to illegal practices and lack of proper clothing and breathing masks.

  • Visual pollution.

Page 37:

  • The Antamina Mine in Peru.

    • Large open-pit mine located high in the Andes Mountains of Peru.

    • Estimated reserve is 1.5 billion tonnes of ore.

    • Extraction of copper and zinc ores began in 2001.

    • More reserves have been found, extending the expected life of the mine to 2029.

Page 38:

  • Economic impacts of mining:

    • Employment.

    • Taxes to government.

    • Transport and services (healthcare, education).

Page 39:

  • Managing the impact of rock and mineral extraction:

    • Safe disposal of mining waste.

    • Land restoration and bioremediation.

Page 40:

  • Safe disposal of mining waste:

    • Piles of wastes with toxic chemicals can cause water and land pollution.

    • Proper mining application should show how mining wastes are stored and disposed of, and steps for preventing water pollution.

Page 41:

  • Land restoration and bioremediation:

    • Waste can be covered with fertilizers to plant trees and allow animals to colonize, creating new landforms.

    • Bioremediation can be used to promote the growth of roots and restore the land.

Page 42:

  • Different methods of bioremediation:

    • Phytoremediation.

    • Phytovolatilization.

    • Phytodegradation.

    • Phytostimulation.

    • Phytostabilization.

    • Rhizofiltration.

Page 43:

  • Post-treatment of mined plots:

    • Land can turn into a nature reserve.

    • Farming or building houses.

    • Introduction of trees and herbs to create habitats for plants and animals.

    • Human recreation.

    • Maintain biodiversity.

Page 44:

  • Sustainable use of rocks and minerals:

    • Find substitutes.

    • Increase efficiency of extraction.

    • Recycling materials.

    • Pass laws for recycling and reuse.

Page 45:

  • Sustainable use of rocks and minerals:

    • Recycling materials.

    • Find substitutes.

    • Increase efficiency of extraction.

    • Pass laws for recycling and reuse.