(a) Describe the characteristics of each of the following rock types
(i) Granite
(ii) Limestone
(iii) Graphite
(b) Explain how each rock type is formed
Explanation
(a) The characteristics of the following are;
(i) Granite
(i) Granite contains large crystals
(ii) They do not occur in layers or strata
(iii) They do not contain fossils which are the remains of plants and animals embedded in rocks.
Limestone:
(i) Limestone is arranged in layers or stata
(ii) They contain fossils
(iii) The rock is non-crystaline in structure
(iii)Graphite:
(i) Graphite is not crystaline
(ii) It is arranged in layers or strata
(iii) It may contain fossils
(b)(i) Granite is formed from the cooling and solidification of molten magma ejected from below the earth crust. It cools before reaching the surface of the earth hence granite is called a plutonic or intrusive igneous rock
(ii) Limestone is formed from the remains of living organisms such as corals or shellfish. These remains have been cemented together under the influence of water to form organic sedimentary rock
(iii) Graphite is formed from pre-existing sedimentary rock called clay which have changed or metamorphosed to a new rock as a result of the influence of heat and pressure. Graphite is an example of metamorphic rock.