1. Composition and Structure of Minerals After completing this section, students will discover the unique physical characteristics of various minerals (Standard PI – 021)

2. All the rocks of the Earth’s crust consist of minerals A mineral has the following characteristics

3. Minerals occur naturally Minerals are found in the ground, or in water. Halite is formed from dissolved seawater

4. Minerals are solid Many minerals are formed from solidified magma

5. Minerals have a definite chemical composition Sodium chloride is the chemical formula for halite

6. The have atoms arranged in an orderly pattern (form crystals) There are 6 families of crystal families

7. Minerals are inorganic (never alive)

8. 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

9. Most minerals are compounds. A compound is a combination of two or more elements

10. A few minerals consist of single elements and are called native elements Native gold

11. 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

12. These are examples of minerals that form from magma tourmaline basalt plagioclase

13. Some minerals from as water containing dissolved ions slowly evaporates. Sylvite forms from sodium and chlorine ions dissolved in water

14. Still other minerals form from heat, pressure or chemical action Copper ore formed from pressurization