Rocks and Minerals!
A Review of Chemistry!

An atom is the smallest particle of
matter that contains the characteristics
of an element.

An element is a chemical made of all the
same type of atoms.

Types of elements (most common in the
Earth’s crust)
◦
◦
◦
◦
◦
◦
◦
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Oxygen (O)
Silicon (S)
Aluminum (Al)
Iron (Fe)
Calcium (Ca)
Sodium (Na)
Potassium (K)
Magnesium (Mg)

Substance is a material with a specific
chemical composition.

Compound is a pure chemical substance
consisting of two or more different
chemical substances.

Mixture is a collection of molecules or
atoms of different types.
Rocks and Minerals!
 A mineral
is a naturally
occurring, inorganic solid
with an orderly crystalline
structure and definite
chemical composition.

Now let’s look at each part of the
definition in detail!
A mineral is a naturally occurring, inorganic
solid with an orderly crystalline structure and
definite chemical composition.
 Naturally
occurring means
that the mineral was made
by natural geologic
processes over time.
Minerals cannot be made
by humans!
Silicon Wafer: Not Naturally
Occurring!!!
Also, not natural!
A mineral is a naturally occurring, inorganic
solid with an orderly crystalline structure and
definite chemical composition.
 Inorganic
means that it does
not typically contain carbon.
There are a few exceptions
such as calcium carbonate
(limestone).
Peat (partially decomposed
organic material) is not a mineral
A mineral is a naturally occurring, inorganic
solid with an orderly crystalline structure and
definite chemical composition.
 Solid
means that the minerals
are solid within normal
temperatures on the Earth!
(They can be melted or turned
into a liquid if heated up high
enough!)
Tar: Not a solid so not a mineral!
A mineral is a naturally occurring, inorganic
solid with an orderly crystalline structure and
definite chemical composition.
 Orderly
crystalline structure
means that the atoms are
arranged in an orderly and
repetitive manner. There are a
few exceptions to this.
Obsidian (volcanic glass) is
sometimes not considered a
mineral!
A mineral is a naturally occurring, inorganic
solid with an orderly crystalline structure and
definite chemical composition.
 Definite
chemical composition
means that the minerals are
composed of elements that
occur in a consistent ratio.
Halite (NaCl) has a definite
chemical composition!
How Are
Minerals
Formed???

Minerals form almost everywhere in
the Crust under different conditions.
◦ Some minerals form deep within the Crust
and others are formed in shallow
deposits.
◦ Some minerals form in ocean water and
some are made from other minerals that
have been crushed and compressed.

There are four major processes by
which minerals are formed:
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◦
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Crystallization from magma
Precipitation
Changes in pressure and temperature
Formation from hydrothermal solutions.
Crystallization from Magma

As magma (molten rock) cools, the
elements chemically combine to form
minerals.

Usually the iron, calcium and
magnesium minerals crystallize first.
The sodium, potassium and aluminum
minerals will crystallize next.
When the magma cools, the
crystals form.
Precipitation

The water found in oceans, lakes,
streams, and rivers contain dissolved
substances in it. When the water
evaporates, some of the dissolved
substances in the water can react to
form minerals.

Limestone and halite (sodium
chloride) are two minerals formed by
precipitation.
Pressure and Temperature

When existing minerals are subjected
to extreme pressure and
temperatures, new minerals can form.
Marble
Hydrothermal Solution

A hydrothermal solution is a very hot
(between 100⁰ C and 300 ⁰ C) mixture
of water and dissolved substances.

When the solution cools, chemical
reactions can take place to form new
minerals.

Over 3,800 different types of minerals
have been identified and named!

These minerals are classified based on
their composition.

The major classes of minerals on earth
are:
◦ Silicates, carbonates, oxides,
sulfates/sulfides, halides, and native
elements.
◦ Can you guess what element each of these
groups contain?