Minerals in the Earths Crust
•Different types of rock in the earths surface contain different minerals. These minerals are formed by either sedimentation, dissolving, evaporation, erosion or mountain building.
•Chemical industries grow near where these minerals are found.
is a sedimentary rock, it’s grey/white and contains mainly of calcium carbonate. (sedimentary rock is formed by layers of sediment laid down in lakes/seas.)
•Sediment comes from shells, bones or sea creatures or erosion from existing rock.
•Erosion creates tiny particles of sediment that wash away and end up at the bottom of a sea or lake. Over millions of years the layers of sediment get buried under more, the weight of this squeezes out the water.
• Fluids flowing through pores in the sediment deposit natural mineral cement that holds the sediment particles together to form rock.
Minerals in the Earths Crust 2
Coal is another type of sedimentary rock, it’s black in colour and formed over millions of years by fossilisation of layers of plant matter. Its mainly the element of carbon. Some types of coal are hard because they’re put under high pressure and temperatures (this can happen during the mountain building process). Salt is left by evaporation. Salt is extracted by underground deposits. These were formed when ancient seas containing salt evaporated. The salt left was buried by other layers of sediment over millions of years. This is deposits of rock salt.
Salt is found in Underground Salt Deposits
Rock Salt is a nixture of salt and impurities and is found in underground deposits.
It can be extracted by normal mining, soultion mining or from the sea.
Normal Salt Mining-
Rock salt is drilled, blasted and dug out and brought to the surface using machinery, most rock salt obtained through this type of mining is used on roads to stop ice forming (grit), The salt can also be separated out and used to enhance the flavour in food or for making chemicals.
Water is injected into the salt deposit through the outer pipe which dissolves the salt to make brine (a salt and water solution), pressure forces the brine up to the surface through the inner pipe, the brine is then stored in wells above the surface and pumped to a refining plant, where it is needed. Impurities are removed from the brine in the refining plant and its then pumped into containers, The brine is boiled and the water evaporates leaving the salt behind, used for most table salt and chemical production.
Both types of mining have an impact on the environment
- land above disused mines can collapse into the holes- (subsidence)
-Mining uses a lot of energy, which usually comes from burning fossil fuels, so it uses non-renewable resources and produces pollution.
Salt obtained from the sea
Hot countries like Australia and China can obtain salt by evaporating sea water. Sea water flows into specially built shallow pools and is left to evaporate in the sun, leaving the salt behind. This process is repeated several times and then the salt is collected.
This method creates the purest of salt- it can be nearly 100% sodium chloride.
Salt in the food industry
Uses of salt in the food production;
Salt is added to most processed foods to enhance the flavour. It is also used as a preservative which is something thats added to foods to give them a longer life before they "go off" due to the action of mould or bacteria.
Eating too much salt can cause high blood pressure for about 30% of the UK population and high blood pressure can lead to strokes and heart attacks. There is also evidence to suggest that eating too much salt can increase the chance of getting stomach cancer, osteoporosis and renal failure.
Food Standards Agency provide advice to the government and public about food safety and health. They issue Guideline Daily Amounts (GDA) that show the maximum amount of salt that people should have per day depending on their age. Department of health= carry out risk assessments for chemicals in food to make sure they're safe and advise the public about how food affects health.