Theory question 204
Rocks(a) Describe four characteristics of igneous rocks (b) Using specific examples, state four ways in which metamorphic rocks are useful to man.
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(a) Formed from cooled and solidified magma or lava; crystalline (large crystals when cooled slowly underground, e.g. granite; small or glassy when cooled fast at the surface, e.g. basalt); not in layers (unstratified); contain no fossils; hard and resistant, mostly impermeable; may be acidic (light coloured, rich in silica) or basic (dark); intrusive or extrusive.
(b) Marble for building, floor tiles and sculpture; slate for roofing and blackboards; graphite for pencils and lubricants; gneiss and quartzite for construction and road stone; precious stones such as diamonds and emeralds for jewellery; exports earn foreign exchange; tourist sites.
Give a named example with each use.