Rocks Examples
Sedimentary rocks Coal, limestone, chalk, gypsum, clay, etc
Metamorphic rocks Slate, marble, graphite, quartzite, schist, gneiss, etc
(b) The main differences between sedimentary rocks and metamorphic rocks are as follows:
(i) Permeability: Sedimentary rocks are more permeable while metamorphic rocks are more impervious.
(ii) Fossils; The fossils in metamorphic rocks have been destroyed by heat and pressure while sedimentary rocks have beautiful fossils
(iii) Jointing: The sedimentary rocks are more jointed than the metamorphic rocks
(v) Mineralogy: Metamorphic rocks contain non-ferrous minerals while sedimentary rocks contain hydrocarbons as minerals
(vi) Lustres: Metamorphic rocks are crystaline while sedimentary rocks are non-crystaline
(vii) Relief: Sedimentary rocks generally subtend lower relief than metamorphic rocks
(viii) Mode of formation: Metamorphic rocks are formed due to heat and intense pressure while sedimentary rocks are formed through deposition of weathered materials, remains of organic matter and evaporation of chemically charged water. Metamorphic rocks are formed out of existing rocks whereas sedimentary rocks are products of weathering.