Geology Revision

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• The mining Industry plays an important part in Australia's economy. Minerals containing metals of value are called mineral ores. Geologists use satellite information, geological studies and chemical analysis of the water and soil to find vast quantities of mineral ores.

1. EIS

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   • before mining can begin an Environmental impact statement need to be prepared. this outlines how the company must protect the environment while mining as well as how the company must rehabilitate the land after mining is finished.
2. Mining methods

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   • Open-cut mining removes the topsoil and overburden in order to get the mineral ore. Underground mining involves the diggeing of shafts and tunnels. this is more dangerous and expensive
3. Getting the Metal

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   • To obtain the metal first the mineral ore is removed from the rock, this involves crushing, grinding and washing. Then the metal is extracted from the minerals by chemical means.

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• Any naturally occurring solid with a definite chemical structure is called a mineral.Native elements like diamond and gold are also minerals. Most minerals are compounds of oxygen and silicon. The atoms join to form crystals, larger crystals form from slow cooling. The way crystals grow depends on speed of cooling, space available and the molten material used.

1. IdentifyMinerals
   1. Colour
   2. Lustre

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      • This describes the way light is reflected from the mineral (eg) dull,pearly, waxy, silky, metallic, glassy or brilliant.
   3. Streak

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      • This is the powdery mark left by the mineral when scratched along a solid surface.
   4. Hardness

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      • The hardness is determined by scratching one mineral off another, the softer mineral gets scratched. Friedrich Mohs' scale of hardness is a numbered scale comparing 10 minerals in order of hardness.

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• Rocks can change from one type to another using heating,cooling, pressure, weathering and erosion and remelting.

1. Igneous

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   • Igneous rocks are all made from cooled magma or lava.
   1. Extrusive

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      • Igneous rocks made by cooling lava above ground. Their appearance depends on how quickly the lava cools and what substances are in the lava.
      1. Pumice

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         • Pale colour rock, full of holes due to lava cooling while full of gases. Floats on water. Used in abrasive cleaners.
      2. Scoria

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         • Heavier and darker than pumice due to presence of iron. Red-brown in colour and holey. Used in garden paths.
      3. Basalt

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         • Has many appearances due to different cooling speeds and hence crystal size. Basalt with bubbles is rough and holey and has large crystals. Pillow Basalt formed underwater and is smooth and rounded with small crystals.
      4. Obsidian

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         • Smooth black rock with no crystals as it cools so rapidly.
   2. Intrusive

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      • Igneous rocks formed under ground. Slow cooling leads to big crystals. Large areas called Batholiths.
      1. Granite

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         • Large crystals of quartz, mica and feldspar are easily seen by the naked eye. Very hard. Used in buildings, headstones, kitchen counters.
2. Sedimentary

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   • Formed from sediments of other rocks made by weathering. sediments are deposited due to erosion by ice, wind and water. deposited sediment is squashed or compressed. Compressed sediment gets stuck together by salts left by evaporated water, this is called cementation.
   1. Chalk

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      • Formed from small grains of calcium carbonate that separated from sea water. The White Cliffs of Dover in England are made from chalk. Use for writing etc.
   2. Limestone

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      • Formed from the remains of marine organisms like shellfish and corals. mainly calcium carbonate. Used for building and makes Lime for concrete and use on land.
   3. Coal

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      • Formed from the remains of dead plants. used for fuel and electricity production
   4. Sandstone

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      • formed from grains of sand cemented together. Used in buildings.
   5. Mudstone

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      • Formed from fine grains of sediment deposited by calm waters. used in garden decoration.
   6. Shale

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      • Formed from the fine grains deposited by slow moving water. Used in garden decoration.
   7. Siltstone

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      • Formed by small mud sediments.
   8. Conglomerate

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      • Formed from different sized grains deposited by fast flowing or flooding rivers. Used for decorative pourposes.
3. Metamorphic

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   • Formed by Igneous and sedimentary rocks when exposed to heat or pressure.
   1. Slate

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      • Formed when shale is exposed to pressure. used for roofing and pool tables.
   2. Quartzite

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      • Formed when sandstone is exposed to heat.
   3. Marble

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      • made when limestone is exposed to heat. used fro buildings and statues.
   4. Gneiss

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      • Formed due to pressure on granite.

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• A fossil is evidence of living things preserved in rocks. Scientists that study fossils are called palaeontologists. By comparing fossils they can compare the relative ages of rocks. Some animal and plant remains are eaten or destroyed over time but some are preserved and fossilised.

1. Hard Parts

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   • Wood, shell, teeth and bones an be chemically changed by the minerals in the water around them. Fossils like this keep their original shape but have been changed chemically.
2. Whole Bodies

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   • Sometimes the hard and soft parts of the body can be fully preserved by becoming trapped in sap/amber or compacted ice or mud pools.
3. Impressions

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   • Animal and plant remains can leave an impression/imprint in sediments. Sometimes trapped remains break down but leave the mould in the shape of the organism.
4. Trace Fossils

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   • Trace fossils provide signs of the presence of the organism eg footprints and plant, leaf and root impressions.
5. Dinosaur Riddle

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   • between 250 million and 65 million years ago dinosaurs were the most successful animals on earth. There are several theories about how they became extinct 1. Asteroid theory 2. Volcano theory 3. Cooling Climate Theory 4. Emerging Plant Theory