Prentice Hall EARTH SCIENCE

Tarbuck Lutgens

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Chapter �4

Minerals vocab

Alloy

Alteration

Carbonate

Cleavage

Compound

Crystal

Crystal form

Crystallization

Density

Element

Fracture

Gem

Halide

Hardness

Lava

Luster

Magma

Mineral

Mohs Hardness Scale

Native Element

Ore

Oxide

Place deposit

Rock

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Silicate

Streak

Sulfate

Sulfide

Matter

◆ Elements are the basic building blocks of minerals.

◆ 118 elements are known.

Matter

◆ Smallest particles of matter

• neutrons, which have neutral electrical charges
• electrons, which have negative electrical charges

◆ The nucleus is the central part of an atom and contains

• protons, which have positive electrical charges

Matter

◆ Energy levels, or shells

• surround the nucleus

• contain electrons—negatively charged particles

◆ The atomic number is the number of protons in the nucleus of an atom.

Model of an Atom

Model of an Atom

Model of an Atom

Matter

◆ Many isotopes are radioactive and emit energy and particles.

◆ Isotopes of an element have the same number of protons but varying numbers of neutrons.

◆ Have different mass numbers: the sum of the neutrons plus protons

◆ The mass number is the number of neutrons and protons in the nucleus of an atom.

Matter

• A compound consists of two or more elements that are chemically combined in specific proportions.

◆ When an atom’s outermost energy level does not contain the maximum number of electrons, the atom is likely to form a chemical bond with one or more atoms.

• An ion is an atom that gains or loses electrons.

Matter

1. Ionic bonds form between positive and negative ions.

2. Covalent bonds form when atoms share electrons.

3. Metallic bonds form when metal ions share electrons.

Minerals

1. Naturally occurring

2. Solid substance

3. Orderly crystalline structure

4. Definite chemical composition

5. Generally considered inorganic

Minerals

2. Crystallization from magma

3. Precipitation

4. Pressure and temperature

5. Hydrothermal solutions

1. Evaporation

Minerals Formed as a Result of Crystallization of Magma

Minerals

◆ Can be classified based on their composition

1. Silicates

• Silicon and oxygen combine to form a structure called the silicon-oxygen tetrahedron. This silicon-oxygen tetrahedron provides the framework of every silicate mineral.

The Silicon-Oxygen Tetrahedron

Silicon-Oxygen Chains, Sheets, �and Three-Dimensional Networks

Minerals

2. Carbonates

• Minerals that contain the elements carbon, oxygen, and one or more other metallic elements

3. Oxides

• Minerals that contain oxygen and one or more other elements, which are usually metals

Carbonate

Oxide

Minerals

4. Sulfates and Sulfides

• Minerals that contain the element sulfur

5. Halides

• Minerals that contain a halogen ion plus one or more other elements

6. Native elements

• Minerals that exist in relatively pure form

Sulfides

halide

Native Copper

Properties of Minerals

◆ Small amounts of different elements can give the same mineral different colors.

Color

Azurite is blue

Properties of Minerals

◆ Streak is the color of a mineral in its powdered form.

Streak

Pyrite is brown/black, Rhodochrosite is white

Properties of Minerals

◆ Luster is used to describe how light is reflected from the surface of a mineral.

Properties of Minerals

Pyrite: metallic

Topaz: Glassy

Kaolinite: Dull

2.3 Properties of Minerals

◆ Luster is used to describe how light is reflected from the surface of a mineral.

2.3 Properties of Minerals

◆ Crystal form is the visible expression �of a mineral’s internal arrangement of atoms.

2.3 Properties of Minerals

Quartz Often Exhibits �Good Crystal Form.

2.3 Properties of Minerals

◆ Hardness is a measure of the resistance of a mineral to being scratched.

◆ Mohs scale consists of 10 minerals arranged from 10 (hardest) to 1 (softest).

Mohs Scale of Hardness

Properties of Minerals

◆ Cleavage is the tendency of a mineral to cleave, or break, along flat, even surfaces.

Properties of Minerals

Properties of Minerals

Mica Has Cleavage in One Direction

Properties of Minerals

◆ Minerals that do not show cleavage when broken are said to fracture.

◆ Fracture—the uneven breakage of �a mineral

Conchoidal Fracture

Properties of Minerals

◆ Density is a property of all matter that �is the ratio of an object’s mass to its volume.

Properties of Minerals

◆ Some minerals can be recognized by other distinctive properties.

The Rock Cycle

◆ Rocks are any solid mass of mineral or mineral-like matter occurring naturally as part of our planet.

◆ Types of Rocks

1. Igneous rock is formed by the crystallization of molten magma/lava.

The Rock Cycle

Intrusive Rocks: Formed from the cooling and crystallization of Magma.

Extrusive Rocks: Formed from the cooling of Lava on the surface of the Earth.

The Rock Cycle

The Rock Cycle

◆ Types of Rocks

2. Sedimentary rock is formed from the weathered products of pre-existing rocks that have been transported, deposited, compacted, and cemented.

3. Metamorphic rock is formed by the alteration of pre-existing rock deep within Earth (but still in the solid state) by heat, pressure, and/or chemically active fluids.

The Rock Cycle

◆ Shows the interrelationships among the three rock types (igneous, sedimentary, and metamorphic)

◆ Magma is molten material that forms deep beneath the Earth’s surface.

◆ Lava is magma that reaches the surface.

◆ Weathering is a process in which rocks are broken down by water, air, and living things.

◆ Sediment is weathered pieces of Earth elements.

The Rock Cycle

3.1 The Rock Cycle

◆ Processes driven by heat from the Earth’s interior are responsible for forming both igneous rock and metamorphic rock.

◆ External processes produce sedimentary rocks.

◆ Weathering and the movement of weathered materials are external processes powered by energy from the sun.

3.2 Igneous Rocks

1. Texture

◆ Igneous rocks can be classified based on their composition and texture.

• Coarse-grained texture is caused by slow cooling resulting in larger crystals.

• Fine-grained texture is caused by rapid cooling resulting in smaller, interconnected mineral grains.

Course-Grained Igneous Texture

Course-Grained Igneous Texture

Fine-Grained Igneous Texture

3.2 Igneous Rocks

1. Texture (continued)

• Glassy texture is caused by very rapid cooling.

• Porphyritic texture is caused by different rates of cooling resulting in varied sized minerals.

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Obsidian Exhibits a Glassy Texture.

Porphyritic Igneous Texture

Porphyritic Igneous Texture

3.2 Igneous Rocks

2. Composition

• Mafic: low amounts of silica (50% or below) Flows easily. High heat. dark colored

3.2 Igneous Rocks

2. Composition (continued)

• Felsic: Hight concertation of silica (70%). High viscosity (sticky, doesn’t flow well). Light colored

3.2 Igneous Rocks

2. Composition (continued)

• Intermediate. Silica about 60%.

Basalt

Andesitic

Classification of Igneous Rocks

Felsic Inter. Mafic

3.3 Sedimentary Rocks

• Erosion involves the weathering and the removal of rock.

• Deposition occurs when an agent of erosion—water, wind, ice, or gravity—loses energy and drops sediments.

◆ Weathering, Erosion, and Deposition

3.3 Sedimentary Rocks

• Compaction is a process that squeezes, or compacts, sediments.

• Cementation takes place when dissolved minerals are deposited in the tiny spaces among the sediments.

◆ Compaction and Cementation

3.3 Sedimentary Rocks

1. Clastic sedimentary rocks are composed �of weathered bits of rocks and minerals.

• Classified by particle size

◆ Two Main Groups

- Shale (most abundant)

• Common rocks include

- Conglomerate

- Sandstone

Shale with Plant Fossils

Conglomerate

3.3 Sedimentary Rocks

◆ Two Main Groups

2. Chemical sedimentary rocks form when dissolved substances precipitate, or separate, from water.

• Common rocks include

- limestone—most abundant chemical rock

- microcrystalline quartz known as chert, flint, jasper, or agate

- evaporites such as rock salt or gypsum

- coal

Fossiliferous Limestone

Classification of �Sedimentary Rocks

3.4 Metamorphic Rocks

◆ Metamorphism means “The process of change.”

◆ Conditions for formation are found a few kilometers below the Earth’s surface and extend into the upper mantle.

◆ Most metamorphic changes occur at elevated temperatures and pressures.

3.4 Metamorphic Rocks

◆ Contact metamorphism occurs when magma moves into rock.

• Changes are driven by a rise in temperature.

• Occurs near a body of magma

3.4 Metamorphic Rocks

◆ Regional metamorphism results in large-scale deformation and high-grade metamorphism.

• Directed pressures and high temperatures occur during mountain building.

• Produces the greatest volume of metamorphic rock

3.4 Metamorphic Rocks

3.4 Metamorphic Rocks

3.4 Metamorphic Rocks

◆ Heat

◆ Pressure

• Provides the energy needed to drive chemical reactions

• Causes a more compact rock with greater density

Origin of Pressure in Metamorphism

Origin of Pressure in Metamorphism

3.4 Metamorphic Rocks

• Hot water-based solutions escaping from the mass of magma

• Promote recrystallization by dissolving original minerals and then depositing new ones

◆ Hydrothermal Solutions

3.4 Metamorphic Rocks

1. Foliated Metamorphic Rock

2. Nonfoliated Metamorphic Rock

◆ Two main categories

• Has a banded or layered appearance

• Does not have a banded texture

Schist and Gneiss

Slate and Phyllite

Marble

Marble

Quartzite

Quartzite

Anthracite

Classification of Metamorphic Rocks