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Lecture No. 3
Crystals and Minerals

The composition of the earth's crust:
The earth's crust is made of minerals and rocks, and crystal is the unit of
mineral formation, and mineral is the unit of rock composition, meaning
that any rock of the earth's crust is usually composed of two or more
minerals, as well as a mineral of several crystals.
Although the elements that enter into the formation of the earth’s crust
are numerous, about a hundred, we find that only about nine of these
elements make up more than 99% of the contents of the earth’s crust, as
many other elements such as gold, tin and copper are very rare in
ordinary rocks and are concentrated only in the private places.
It is clear that oxygen is the most prevalent element in the earth’s crust
and this does not mean that this gas is free in the crust, but it is
chemically united in different rocks with other elements, and the same is
true of other elements, there is no free elemental state in Rocks, but they
are all combined with oxygen and with other elements in the form of
chemical compounds.
Natural mineral composition
Minerals are formed in the earth's crust in several ways:
* Method of crystallization of magma
Some minerals form from molten lava or molten rock called magma in
the same way that ice crystals form when water freezes and slow cooling
helps to form large crystals.