Composition and Structure of Minerals

After completing this section, students will discover the unique physical characteristics of various

minerals (Standard PI – 021)

All the rocks of the Earth’s crust consist of minerals

A mineral has the following characteristics

Minerals occur naturally

Minerals are found in the ground, or in water. Halite is formed from dissolved

seawater

Minerals are solid

Many minerals are formed from solidified magma

Minerals have a definite chemical composition

Sodium chloride is the chemical formula for halite

The have atoms arranged in an orderly pattern (form crystals)

There are 6 families of crystal families

Minerals are inorganic (never alive)

There are over 4000 known minerals. But 8 minerals make up

98% of the earth’s crust

More than 90% of the minerals in the earth’s crust are compounds containing oxygen and

silicon

Most minerals are compounds. A compound is a combination of

two or more elements

A few minerals consist of single elements and are called native

elements

Native gold

Minerals can form in many ways. Some form from molten rock

(magma)

As the magma cools, the atoms, ions and molecules move closer together and form chemical bonds that create compounds

These are examples of minerals that form from magma

tourmaline

basalt

plagioclase

Some minerals from as water containing dissolved ions slowly

evaporates.

Sylvite forms from sodium and chlorine ions dissolved in water

Still other minerals form from heat, pressure or chemical

action

Copper ore formed from pressurization