Earth Science

1. 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 • 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.