The outermost part of lithosphere is called crust. This is the most significant part of
the earth because it is occupied by humans. The material of the crust is made up of
rocks. The rocks are of different types. They are hard like granite, soft like clay
and loose like gravel. Rocks have a great variety of colour, weight and hardness.
Rocks are composed of minerals. They are aggregates or physical mixture of one
or more minerals. Minerals on the other hand are made up of two or more elements
in a definite ratio. They have a definite chemical composition. Crust is made
up of more than 2000 minerals, but out of these, 6 are the most abundant and
contribute the maximum to this uppermost part of the earth. These are feldspar,
quartz, pyroxenes, amphiboles, mica and olivine.
Granite is a rock and its constituent minerals bound together are quartz, feldspar
and mica which make it a hard rock. Change in the ratio of these minerals give rise
to granites of different colours and hardness. The minerals containing metals are
called metallic minerals. Haematite, a major iron ore is a metallic mineral. Ores are
metallic minerals which can be profitably mined. Rocks are of immense economic
importance to us
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