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• identify common rock forming minerals The geology of a given area, particularly the rocks and minerals, plays a large role in the local environment. Rocks and minerals break down to form soils. The minerals and nutrients in a particular soil influences what sorts of plants and therefore animals will occur in an area. Most rocks are formed from one or more minerals. Minerals are inorganic substances with specific physical and chemical properties. Minerals can be used to identify rocks and soils. Approximately 95% of minerals are silicates which contain silicon (Si) and oxygen (O) atoms bonded together. Oxygen (46%) and silicon (28%) are the two most abundant elements in the Earth’s crust. Carbonates contain CO3 molecules. Sulfates contain S04 molecules, sulfides contain elemental sulfur (S). Oxides of iron and aluminium are relatively common, e.g. haematite. Hardness: is the ability to resist scratching. Diamond has a hardness of 10, talc has a hardness of 1 (Moh’s scale of hardness). Lustre: describes the way a mineral reflects light, e.g. dull, vitreous (shiny) Colour: some minerals (e.g. quartz) can be variable in colour, however some minerals (e.g. olivine) can have consistent colour Cleavage: refers to how a mineral naturally breaks or splits. Cleavage can occur in one, two or three planes (see fig. 3.2.4, p. 132). Density: is the objects mass divided by it’s volume, usually in g/cm3. Texture: refers to the size of crystals in a mineral, small crystals will feel smooth, larger crystals will usually feel rough. Email or submit by 9am Monday 7/2/11 Questions 1,3,4,8 on p. 131. Questions 1,2,3,5,6,9 on p. 133.