3 Minerals of the Earth’s Crust SECTION 1 What Is a …internet.savannah.chatham.k12.ga.us/schools/gss/gradelevels/6th...Interactive Textbook 37 Minerals of the Earth’s Crust SECTION1

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Interactive Textbook 37 Minerals of the Earth’s Crust

SECTION

1 What Is a Mineral?Minerals of the Earth’s Crust

Name Class Date

CHAPTER 3

After you read this section, you should be able to answer these questions:

• What are minerals?

• What determines the shape of a mineral?

• What are two main groups of minerals?

What Are Minerals?A mineral is a naturally formed, inorganic solid that

forms crystals and is always made of the same elements. The figure below shows four questions that you can ask in order to learn whether something is a mineral.

Is it nonliving?Minerals are inorganic.

This means that they are not made of living things

or their remains.

Is it a solid?Minerals are not gases or liquids.

Does it have a crystalline structure?Minerals are crystals. Each mineral has a

certain crystal structure that is always the same.

Does it form naturally?

Minerals are not made by people.

All minerals have four features, as described in the fi gure.

You might not be familiar with the term “crystalline structure.” To understand what crystalline structure is, you need to know a little about how elements form minerals. Elements are pure substances that cannot be broken down into simpler substances. Oxygen, chlorine, carbon, and iron are examples of elements. Elements can come together in certain ways to form new substances, such as minerals. All minerals are made of one or more elements.

BEFORE YOU READ

STUDY TIPLearn New Words As you read, underline words you don’t understand. When you fi gure out what they mean, write the words and their defi nitions in your notebook.

TAKE A LOOK 1. Explain Why are diamonds that are made by people not considered minerals?

Critical Thinking2. Apply Concepts Coal is made from the remains of dead plants. Is coal a mineral? Explain your answer.



SECTION 1

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What Is a Mineral? continued

COMPOUNDS AND ATOMS Most minerals are made of compounds of several dif-

ferent elements. A compound is a substance made of two or more elements that are chemically bonded. For example, the mineral halite is a compound of sodium, Na, and chlorine, Cl. A few minerals, such as gold and silver, are made of only one element. A mineral that is made of only one element is called a native element.

Each element is made of only one kind of atom. An atom is the smallest part of an element that has the prop-erties of that element. Like other compounds, minerals are made up of atoms of one or more elements.

CRYSTALSRemember that minerals have a definite crystalline

structure. This means that the atoms in the mineral line up in a regular pattern. The regular pattern of the atoms in a mineral causes the mineral to form crystals. Crystals

are solid, geometric forms of minerals that are formed by repeating a pattern of atoms.

The shape of a crystal depends on how the atoms in it are arranged. The atoms that make up each mineral are different. However, there are only a few ways that atoms can be arranged. Therefore, the crystals of different min-erals can have similar shapes.

Although different minerals may form similar shapes, each mineral forms only one shape of crystal. Therefore, geologists say that a mineral has a definite crystalline structure. This means that crystals of a certain mineral always form the same shape.

The mineral gold is made of atoms of the element gold. The atoms are arranged in a cubic pattern.

Crystals of gold form cubes because of the way their atoms are arranged.

Real crystals of gold may not be perfect cubes because the crystals may be damaged or not form completely. However, the atoms are still arranged in a cubic pattern.

READING CHECK

3. Defi ne What is a compound?

READING CHECK

4. Explain What causes minerals to form crystals?

TAKE A LOOK 5. Identify What shape are gold crystals?



SECTION 1

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What Is a Mineral? continued

How Do Geologists Classify Minerals?Geologists classify minerals based on the elements or

compounds in the minerals. Two main groups of minerals are silicate minerals and nonsilicate minerals.

SILICATE MINERALSSilicon and oxygen are two of the most common elements

in the Earth’s crust. Minerals that contain compounds of silicon and oxygen are called silicate minerals. Silicate minerals make up more than 90% of the Earth’s crust. Most silicate minerals also contain elements other than silicon and oxygen, such as aluminum, iron, or magnesium.

Common Silicate Minerals

Mica breaks into sheets easily.

Quartz is a mineral that is found in many rocks of the Earth’s crust.

Feldspar is also common in the rocks of the Earth’s crust. Feldspar can contain many elements other than silicon and oxygen, such as potassium or sodium.

NONSILICATE MINERALSMinerals that do not contain compounds of silicon and

oxygen are called nonsilicate minerals. Some of these minerals are made of elements such as carbon, oxygen, fluorine, and sulfur.

Types of Nonsilicate Minerals

Copper

Calcite

Fluorite Galena

Gypsum

Corundum

Native elements are minerals that are made of only one element. Copper, gold, silver, and diamonds are native elements.

Oxides are minerals that contain com-pounds of oxygen and another element, such as iron or aluminum. Rubies and sapphires are forms of the min-eral corundum, which is an oxide mineral.

Halides are miner-als that contain the elements fl uorine, chlorine, iodine, or bromine. Fluorite and halite are halide minerals.

Carbonates are minerals that contain compounds of carbon and oxygen. Calcite is a carbonate mineral.

Sulfi des are minerals that contain compounds of sulfur and an element other than oxygen, such as lead, iron, or nickel. Galena and pyrite (“fool’s gold”) are sulfi de minerals.

Sulfates are minerals that contain compounds of oxygen and sulfur. Gypsum is a sulfate mineral.

TAKE A LOOK 6. Identify What two elements are found in all of the minerals in the fi gure? Explain your answer.

TAKE A LOOK 7. Compare How are sulfate minerals different from sulfi de minerals?



Name Class Date

Section 1 Review SECTION VOCABULARY

compound a substance made up of atoms of two or more different elements joined by chemical bonds

crystal a solid whose atoms, ions, or molecules are arranged in a regular, repeating pattern

element a substance that cannot be separated or broken down into simpler substances by chemical means

mineral a naturally formed, inorganic solid that has a defi nite chemical structure

nonsilicate mineral a mineral that does not contain compounds of silicon and oxygen

silicate mineral a mineral that contains a combination of silicon and oxygen and that may also contain one or more metals

1. Identify What are four features of a mineral?

2. Compare What is the difference between an atom and an element?

3. Infer What determines the shape of a crystal?

4. Apply Concepts Why is the ice in a glacier considered a mineral, but the water in a river is not considered a mineral?

5. Describe What are the features of the two major groups of minerals?

6. List Give four types of nonsilicate minerals.



SECTION

2 Identifying MineralsMinerals of the Earth’s Crust

Name Class Date

CHAPTER 3


• What seven properties can be used to identify a mineral?

• What are some special properties of minerals?

How Can You Identify Minerals?If you close your eyes and taste different foods, you can

usually figure out what the foods are. You can identify foods by noting their properties, such as texture and flavor. Minerals also have properties that you can use to identify them.

COLORThe same mineral can have many different colors. For

example, the mineral quartz can be clear, white, pink, or purple. Minerals can also change colors when they react with air or water. For example, pyrite (“fool’s gold”) has a golden color. If pyrite is exposed to air and water, it can turn brown or black. Because the color of a mineral can vary a lot, color is not the best way to identify a mineral.

LUSTERThe way a surface reflects light is called luster. When

you say that something looks shiny, you are describing its luster. A mineral can have a metallic, submetallic, or non-metallic luster. The table below gives some examples of different kinds of luster.

Luster Description Examples

Metallic bright and shiny, like metal gold, copper wire

Submetallic dull, but refl ective graphite (pencil “lead”)

Nonmetallic

Vitreous glassy, brilliant glass, quartz

Waxy greasy, oily wax, halite

Silky looks like light is refl ecting off long fi bers

satin fabric, asbestos

Pearly creamy pearls, talc

Resinous looks like plastic plastic, sulfur

Earthy rough, dull concrete, clay

BEFORE YOU READ

STUDY TIP

Reading Organizer As you read this section, create an outline of the section. Use the properties of minerals to form the headings of your outline.

READING CHECK

1. Explain How can the color of a mineral change?

Say ItApply Ideas In a small group, think of a list of 10 to 15 everyday materials. Together, try to describe the luster of each material using the terms in the table.



SECTION 2

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Identifying Minerals continued

STREAKThe color of a mineral in powdered form is called its

streak. You can find a mineral’s streak by rubbing the mineral against a piece of unglazed porcelain. The piece of unglazed porcelain is called a streak plate. The mark left on the streak plate is the streak.

Streak is a more useful property than color for iden-tifying minerals. This is because the color of a mineral’s streak is always the same. For example, the color of the mineral hematite may vary, but its streak will always be red-brown.

CLEAVAGE AND FRACTUREDifferent minerals break in different ways. The way that a

mineral breaks depends on how its atoms are arranged. When some minerals break, the surfaces that form are smooth and flat. These minerals show the property of cleavage. Other minerals break unevenly, along curved or rough surfaces. These minerals show the property of fracture.

The mineral halite also shows the property of cleavage. Its crystals break into cubes.

The mineral biotite, a type of mica, shows the property of cleavage. It breaks easily into thin, flat sheets.

The mineral quartz shows the property of fracture. It breaks along a curved surface. This kind of frac-ture is called conchoidal fracture.

DENSITYDensity is a measure of how much matter is in a given

amount of space. Density is usually measured in grams per cubic centimeter (g/cm3). For example, the density of water is 1 g/cm3.

Geologists often use specific gravity to describe the density of a mineral. A mineral’s specific gravity is the density of the mineral divided by the density of water. For example, gold has a density of 19 g/cm3. Its specific gravity is 19 g/cm3 � 1 g/cm3 � 19.

READING CHECK

2. Explain Why is streak more useful than color in identifying a mineral?

TAKE A LOOK 3. Identify What kind of fracture does quartz show?

Math Focus4. Calculate How many times denser is gold than water?



SECTION 2

Name Class Date

Identifying Minerals continued

HARDNESS A mineral’s resistance to being scratched is its

hardness. Scientists use the Mohs hardness scale to describe the hardness of minerals. The harder a mineral is to scratch, the higher its rating on the Mohs scale. Talc, one of the softest minerals, has a rating of 1. Diamond, the hardest mineral, has a rating of 10.

Scientists use reference minerals to find the hardness of unknown minerals. They try to scratch the surface of the unknown mineral with the edge of a reference mineral. If the reference mineral scratches the unknown mineral, the reference mineral is harder than the unknown mineral.

You probably don’t have pieces of these reference minerals. However, you can find the hardness of a min-eral using common objects. For example, your fingernail has a hardness of about 2 on the Mohs scale. A piece of window glass has a hardness of about 5.5.

Hardness Mineral Hardness Mineral

1 Talc 6 Orthoclase

2 Gypsum 7 Quartz

3 Calcite 8 Topaz

4 Fluorite 9 Corundum

5 Apatite 10 Diamond

SPECIAL PROPERTIESSome minerals have special properties. These properties

can be useful in identifying the minerals.

Special Properties of Some MineralsCalcite and fl uorite show the property of fl uorescence.This means that they glow under ultraviolet light.

Calciteproduces a chemical reac-tion when a drop of weak acid is placed on it. It fi zzes and produces gas bubbles.

Some miner-als, such as this calcite, show optical proper-ties. Images look doubled when they are viewed through calcite.

Magnetiteshows the property of magnetism.It is a natural magnet.

Halite has a salty taste. You should not taste a mineral unless your teacher tells you to.

Minerals that contain radioac-tive elements may show the property of radioactivity.The radiation they give off can be detected by a Geiger counter.

READING CHECK

5. Defi ne What is hardness?

Critical Thinking6. Apply Concepts A scien-tist tries to scratch a sample of orthoclase with a sample of apatite. Will he be able to scratch the orthoclase? Explain your answer.

TAKE A LOOK 7. Describe Under ultraviolet light, what happens to minerals that show the property of fl uorescence?



Name Class Date

Section 2 Review SECTION VOCABULARY

cleavage in geology, the tendency of a mineral to split along specifi c planes of weakness to form smooth, fl at surfaces

density the ratio of the mass of a substance to the volume of the substance

fracture the manner in which a mineral breaks along either curved or irregular surfaces

hardness a measure of the ability of a mineral to resist scratching

luster the way in which a mineral refl ects lightstreak the color of a mineral in powdered form

1. Compare How are cleavage and fracture different?

2. Explain Why is color not the best property to use to identify a mineral?

3. Identify Give five properties that you can use to identify a mineral.

4. Apply Concepts A geologist has found an unknown mineral. She finds that a sample of calcite will not scratch the unknown mineral. She also finds that a sample of apatite will scratch the unknown mineral. About what is the unknown mineral’s hardness? Explain your answer.

5. Calculate The density of a mineral is 2.6 g/cm3. What is its specific gravity?



SECTION

3 The Formation, Mining, and Use of MineralsMinerals of the Earth’s Crust

Name Class Date

CHAPTER 3


• How do minerals form?

• How are mineral resources used?

How Do Minerals Form?Different minerals form in different environments. The

table below shows five ways that minerals can form.

Process Description Minerals that form this way

Evaporation When a body of salt water dries up, minerals are left behind. As the water evaporates, the minerals crystallize.

gypsum, halite

Metamorphism High temperatures and pressures deep below the ground can cause the minerals in rock to change into different minerals.

garnet, graphite, magnetite, talc

Deposition Surface water and ground water carry dissolved minerals into lakes or seas. The minerals can crystallize on the bottom of the lake or sea.

calcite, dolomite

Reaction Water underground can be heated by hot rock. The hot water can dissolve some minerals and deposit other minerals in their place.

gold, copper, sulfur, pyrite, galena

Cooling Melted rock can cool slowly under Earth’s surface. As the melted rock cools, minerals form.

mica, feldspar, quartz

How Are Minerals Removed from the Earth?People mine many kinds of minerals from the ground

and make them into objects we need. Some minerals have more useful materials in them than others. An ore

is a rock or mineral that contains enough useful materials for it to be mined at a profit.

There are two ways of removing ores from Earth: sur-face mining and subsurface mining. The type of mining used depends on how close the ore is to the surface.

BEFORE YOU READ

STUDY TIPDescribe As you read this section, make a chart show-ing the uses of different rock and mineral resources.

TAKE A LOOK 1. Identify Give three minerals that form by metamorphism and three minerals that form by reaction.Metamorphism:

Reaction:



SECTION 3

Name Class Date

The Formation, Mining, and Use of Minerals continued

SURFACE MININGPeople use surface mining to remove ores that are

near Earth’s surface. Three types of surface mines include open pits, surface coal mines, and quarries.

Open-pit mining is used to remove large, near-surface deposits of gold and copper. Explosives break up the rock layers above the ore. Then, trucks haul the ore from the mine to a processing plant.

Quarries are open mines that are used to remove sand, gravel, and crushed rock. The layers of rock near the sur-face are removed and used to make buildings and roads.

Strip mines are often used to mine coal. The coal is removed in large pieces. These pieces are called strips.The strips of coal may be up to 50 m wide and 1 km long.

SUBSURFACE MININGPeople use subsurface mining to remove ores that are

deep underground. Iron, coal, and salt can be mined in subsurface mines.

READING CHECK

2. Identify Give two minerals that are mined using open-pit mining.

READING CHECK

3. List Give three resources that can be mined using subsurface mining.

TAKE A LOOK 4. Identify What are three kinds of tunnels used in subsurface mining?



SECTION 3

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RESPONSIBLE MININGMining can help us get the resources we need, but it

can also create problems. Mining may destroy or harm the places where plants and animals live. The wastes from mining can be poisonous. They can pollute water and air.

One way to reduce these problems is to return the land to nearly its original state after mining is finished. This is called reclamation. Since the mid-1970s, laws have required the reclamation of land used for mining.

Another way to reduce the problems with mining is to reduce our need for minerals that are mined. For example, when you recycle materials made from minerals, you reduce the need for further mining. If you recycle the aluminum in your soda can, less aluminum has to be removed from the Earth.

How Are Minerals Used?We can use some minerals just as they are. However,

most minerals must be processed before they can be used. The table below shows how some common miner-als are used. The figure on the next page shows some of the processed minerals that are used in a bicycle.

Mineral Uses

Bauxite (aluminum ore) source of aluminum for cans, foil, appliances, and utensils

Copper electrical wire, plumbing, coins

Diamond jewelry, cutting tools, drill bits

Galena (lead ore) source of lead for batteries and ammunition

Gold jewelry, computers, spacecraft

Gypsum plaster, cement, wallboard

Halite table salt, road salt, water softener

Quartz glass, source of silicon for computer chips

Silver photography, electronic products, jewelry

Sphalerite (zinc ore) jet aircraft, spacecraft, paint

READING CHECK

5. Describe What are two problems with mining?

READING CHECK

6. Explain How can recycling help reduce the problems with mining?

TAKE A LOOK 7. Identify Give two uses for the mineral silver and two uses for the mineral bauxite.Silver:

Bauxite:



SECTION 3

Name Class Date


Handlebarstitanium from ilmenite

Framealuminum from bauxite

Pedalsberylliumfrom beryl

Spokesiron from magnetite

Minerals Used in the Parts of a Bicycle

METALLIC MINERALSMany minerals contain metals. Many of the features of

metals make them useful in aircraft, automobiles, com-puter parts, and spacecraft. All metals have the features given below:

• Metals have shiny surfaces.

• Light cannot pass through metals.

• Heat and electricity can pass through metals easily.

• Metals can be rolled into sheets or stretched into wires.

Some metals react easily with air and water. For exam-ple, iron can react with oxygen in the air to produce rust. However, many of these metallic minerals can be pro-cessed into materials that do not react with air and water. For example, iron can be used to make stainless steel, which does not rust. Other metals do not react very eas-ily. For example, gold is used in parts of aircraft because it does not react with many chemicals.

Many metals are strong. Their strength makes them useful in making ships, automobiles, airplanes, and build-ings. For example, tall buildings are too heavy to be sup-ported by a wooden frame. However, steel frames can support skyscrapers that are hundreds of meters tall.

TAKE A LOOK 8. Identify Name four minerals that are used in the parts of a bicycle.

Critical Thinking9. Infer Electricity can pass through metals easily. How does this make metals useful in computers and other electronic appliances?



SECTION 3

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NONMETALLIC MINERALSMany minerals also contain nonmetals. Some important

features of nonmetals are given below:

• Nonmetals can have shiny or dull surfaces.

• Light can pass through some kinds of nonmetals.

• Heat and electricity cannot pass through nonmetals easily.

Nonmetallic minerals are some of the most widely used minerals in industry. For example, the mineral calcite is used to make concrete. The mineral quartz is used to make glass. Quartz can also be processed to produce the element silicon, which is used in computer chips.

GEMSTONESSome nonmetallic minerals are considered valuable

because of their beauty or rarity. These minerals are called gemstones. Important gemstones include diamond, ruby, sapphire, emerald, topaz, and tourmaline.

Color is the feature that determines the value of a gemstone. The more attractive the color, the more valu-able the gemstone is. The colors of many gemstones are caused by impurities. An impurity is a small amount of an element not usually found in the mineral. For exam-ple, rubies and sapphires are both forms of the mineral corundum. Rubies look red because they have chromium impurities. Sapphires look blue because they have iron impurities.

Most gemstones are very hard. This allows them to be cut and polished easily. For example, corundum (rubies and sapphires) and diamond are the two hardest miner-als. They are also some of the most valuable gemstones.

Diamonds are some of the most valuable gemstones. They are used in jewelry and in other items, such as this scepter.

READING CHECK

10. Identify Give two nonmetallic minerals that are used in industry.

READING CHECK

11. Explain What gives many gemstones their color?



Name Class Date

SECTION VOCABULARY

ore a natural material whose concentration of economically valuable minerals is high enough for the material to be mined profi tably

reclamation the process of returning land to its original condition after mining is completed

1. Define Write your own definition for ore.

2. Describe Fill in the spaces in table to describe metals and nonmetals.

Type of material Main features Common objects made from it

metal has shiny surfaces does not transmit lighttransmits heat and electricity easilycan be rolled into sheets or stretched into wires

nonmetal

3. List What are three ways minerals can form?

4. Identify Give three types of surface mines and an example of the kind of material that each is used to mine.

Section 3 Review

Documents

3 Minerals of the Earth’s Crust SECTION 1 What Is a …internet.savannah.chatham.k12.ga.us/schools/gss/gradelevels/6th...Interactive Textbook 37 Minerals of the Earth’s Crust SECTION1