1. Chapter 3 Minerals and Rocks
Earth Science
Chapter 3
Minerals and Rocks

2. Minerals
A mineral is a naturally occurring, solid, inorganic substance that has a definite chemical composition and molecular structure.
Naturally occurring means not made artificially
Inorganic means it is not now, nor ever has been alive.
Minerals are classified on the basis of their physical and chemical properties.

3. Mineral Characteristics
The physical properties of a mineral are due largely to the internal arrangement of atoms.
The six key physical properties that can be seen or easily tested are: color, streak, luster, hardness, and cleavage or fracture.

4. Mineral Characteristics
Color
Most visible property
Color alone is not a good mineral identifier.
Many minerals exhibit the same color.
Many minerals are found in a variety of colors.

5. Mineral Characteristics
Streak
The color of a mineral in its powdered form.
Streak is reliable for mineral identification.
Streak may be different from mineral color.

6. Mineral Characteristics
Luster
The way in which light is reflected from the surface of a mineral.
Minerals with metallic luster shine like polished metals.
Minerals with nonmetallic luster have no metallic shine.
Nonmetallic lusters can be glassy, dull, earthy, etc.

7. Mineral Characteristics
Metallic lusters
Nonmetallic lusters

8. Mineral Characteristics
Hardness
A mineral’s resistance to being scratched
The relative hardness of a mineral is determined by comparing it to the hardness of ten “standard” minerals that make up Moh’s Hardness Scale.
Minerals are often compared to the hardness of glass (5.5).

9. Mineral Characteristics
Cleavage
The tendency of a mineral to split along one or more smooth surfaces or planes.
Mica (1 plane) Halite (3 planes)

10. Mineral Characteristics
Fracture
Minerals that don’t show cleavage, fracture unevenly when they break.

11. Mineral Characteristics
Other properties
Magnetic React with Acid
Salty Taste Bad Odor

12. Formation of Minerals
All minerals are crystalline, or made up of atoms arranged in a pattern.
Minerals are grouped according to their chemical composition.
All minerals are made up of elements.
Minerals are classified based upon the elements they contain.
Most common minerals in the crust are silicates (made of silicon and oxygen).

13. Formation of Minerals
Of all the minerals on the Earth’s crust, over 90% are a combination of the following eight elements:
Percent By Mass in Crust

14. Rocks Most rocks are composed of one or more minerals.
Rocks composed of one mineral are called monominerallic.
Rocks composed of more than one mineral are called polyminerallic.
Most rocks have a number of minerals in common.
Of the over 2,500 different minerals, only 10 to 15 minerals compose 90% of rocks.

15. Rocks Differences between rocks and minerals
Minerals have a uniform composition while the physical properties of rocks vary from one rock to the next.
Minerals are classified by physical properties while rocks are classified by their origin.
Igneous - solidification of molten rock
Sedimentary - compaction and cementation of sediments
Metamorphic - recrystalization of rock

16. Igneous Rocks
Igneous rocks form as a result of the solidification of molten rock material.
Molten rock beneath the Earth’s surface is called magma.
Molten rock that reaches the Earth’s surface is called lava.
When molten rock solidifies, it crystallizes into igneous rock.

17. Igneous Rocks
The texture, or grain appearance, depends on the size and arrangement of crystals.
Intrusive igneous rocks:
Form from magma underground
Solidify slow & have large crystals
Extrusive igneous rocks:
Form from lava above ground
Solidify quick & have small crystals

18. Igneous Rocks
Igneous rocks are grouped according to their mineral composition.
Felsic igneous rocks
Light color
Low density
Most common on continents
Mafic igneous rocks
Dark color
High density
Most common on ocean floor

19. Sedimentary Rocks
Sedimentary rocks form as a result of compaction and cementation of sediments.
Sediments are changed into rock after they are transported and deposited.
Most sedimentary rocks are deposited in large bodies of water.
The presence of sedimentary rocks suggests area was underwater at time of formation.

20. Sedimentary Rocks Compaction Cementation
Pressure created by water and overlying sediments can force particles of sediment close together and compress them into rock.
Cementation
The addition of minerals, such as silica, lime, or iron oxide, tends to glue rock particles together to form solid rock.

21. Sedimentary Rocks Clastic Sedimentary Rock
Formed from sediments made up of rock fragments held together by cement
Layers or cementing material are often visible

22. Sedimentary Rocks Chemical or Crystalline Sedimentary Rocks
Form as a result of chemical processes
Water with dissolved minerals evaporates
Minerals that precipitate out forms crystals
Rock Salt Rock Gypsum

23. Sedimentary Rocks Bioclastic or Organic Sedimentary Rocks
Form from remains of dead organisms.
Coal forms as a result of compression of plant remains.
Limestone can be made of shells.
Coal Limestone

24. Metamorphic Rocks
Metamorphic rocks form as a result of recrystallization of unmelted material under conditions of high temperature and pressure over long periods of time.
Recrystallization is a process in which rocks undergo change without true melting.
As a result of heat and pressure minerals in the rocks combine to form new, larger, denser crystalline structures.

25. Metamorphic Rocks
Banding and foliation of minerals are the most outstanding characteristic of metamorphic rocks.
Due to concentrations of various minerals into zones of different colors
Not to be confused with layering of sedimentary rocks

26. Metamorphic Rocks Types of Metamorphism Contact metamorphism
Molten rock comes in contact with nearby rock
Heat from magma alters the rock it touches
Regional metamorphism
Large areas of rock are under intense heat and pressure
Generally associated with mountain building

27. The Rock Cycle
The rock cycle describes how rocks of all types can be changed into other rocks.
Earliest rocks formed on Earth were igneous
They were uplifted, weathered, and eroded to form sediments.
The sediments were deposited, buried and compacted into sedimentary rocks.
Sedimentary and igneous rocks were subject to heat and pressure to form metamorphic rocks.

28. Mineral Conservation
Today the world’s need for energy resources is greater than ever.
Most energy sources-coal, oil, and natural gas-are nonrenewable (used faster than they can be replaced).
Coal oil and natural gas are called fossil fuels because they are made of the remains of plants and animals that lived long ago.
Fossil fuels and other nonrenewable resources are vital to our everyday lives.

29. Mineral Conservation
Alternate sources of renewable energy resources are under development.
Water power
Wind power
Solar energy
Geothermal energy
The use and distribution of mineral resources have global, financial and political implications.
THEY MUST BE USED WISELY.