minerals · elements, which are chemically pure substances. different minerals combine to form...

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Teacher's Guide

Minerals

Editors:Brian A. Jerome, Ph.D.Stephanie Zak Jerome

Assistant Editors:Anneliese BrownLouise Marrier

Graphics:Fred Thodal

Lyndsey CanfieldDean Ladago

1-800-453-8481Visual Learning CompanyMinerals

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ISBN 978-1-59234-182-5

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Table of Contents2

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A Message from our Company

Viewing Clearances

Use and Copyright

National Standards Correlations

Student Learning Objectives

Assessment

Introducing the Program

Program Viewing Suggestions

Video Script

Answer Key to Student Assessments

Answer Key to Student Activities

Pre-Test

Post-Test

Video Review

Vocabulary

Writing Activity

Making Crystals

Mineral Identifi cation

Exploring Mono Lake


National Standards CorrelationsBenchmarks for Science Literacy(Project 2061 - AAAS)

By the end of the fi fth grade, students should know that:

National Science Education Standards(Content Standards: K-4, National Academy of Sciences)

Grades 3-5

• Rock is composed of different combinations of minerals. Smaller rocks come from the breakage and weathering of bedrock and larger rocks. Soil is made partly from weathered rock, partly from plant remains — and also contains many living organisms.

The Physical Setting - Processes that Shape the Earth (4C)

The Physical Setting - The Structure of Matter (4D)By the end of the fi fth grade, students should know that:

• Materials may be composed of parts that are too small to be seen without magnifi cation.

Earth and Space Science - Content Standard DAs a result of activities in grades K-4, all students should develop an understanding of:

Properties of Earth Materials• Earth materials are solid rocks and soils, water, and the gases of the atmosphere. The varied materials have different physical and chemical properties, which make them useful in different ways, for example, as sources of fuel, or for growing the plants we use as food. Earth materials provide many of the resources that humans use.


Student Learning ObjectivesUpon viewing the video and completing the enclosed student activities, students will be able to do the following:

• Defi ne minerals as naturally occurring solids that have a defi nite chemical makeup and crystal shape.

• Explain that a crystal is made of particles that form a repeating pattern.

• Understand that most minerals are comprised of two or more elements, which are chemically pure substances.

• Differentiate between silicate and nonsilicate minerals and give examples of both.

• List and defi ne different mineral properties, such as color, hardness, streak, and luster.

• Identify common problems associated with classifying or identifying minerals based on their color.

• Explain how Mohs hardness scale can help determine the hardness of minerals.

• Differentiate between cleavage and fracture.

• Explain how minerals are formed from molten rock on or beneath Earth’s surface.

• Understand how changes in temperature or pressure can alter rocks to form different minerals.

• Know that some minerals form when mineral-rich water evaporates.


The Post-Test can be utilized as an assessment tool following student completion of the program and student activities. The results of the Post-Test can be compared against the results of the Preliminary Test to assess student progress.

The Preliminary Test is an assessment tool designed to gain an understanding of students’ preexisting knowledge. It can also be used as a benchmark upon which to assess student progress based on the objectives stated on the previous pages.

Assessment

Preliminary Test (p. 14-15):

Video Review (p. 18):

Post-Test (p. 16-17):

The Video Review can be used as an assessment tool or as a student activity. There are two sections. The fi rst part contains questions displayed during the program. The second part consists of a fi ve-question video quiz to be answered at the end of the video.


Introducing the Program

Program Viewing SuggestionsThe student master “Video Review” is provided (p. 18) for distribution to students. You may choose to have your students complete this Master while viewing the program or do so upon its conclusion.

The program is approximately 14 minutes in length and includes a fi ve-question video quiz. Answers are not provided to the Video Quiz in the video, but are included in this guide on page 12. You may choose to grade student quizzes as an assessment tool or to review the answers in class.

The video is content-rich with numerous vocabulary words. For this reason you may want to periodically stop the video to review and discuss new terminology and concepts.

Before viewing the program, ask students if they know what a mineral is. Explain that minerals are naturally occurring solids that have a defi nite chemical makeup and crystal shape. Minerals are formed by two or more elements, which are chemically pure substances. Different minerals combine to form rocks.

Next, ask students to identify minerals they use everyday. Record the list generated by the class on the board. If students need help getting started, consider offering the following examples: The mineral graphite is used to make the lead of pencils. The wiring of most electronics is made of the mineral copper. Quartz is a raw material of glass and can be found in mirrors, the face of wrist watches, lightbulbs, and drinking glasses. Salt is a mineral that is used to add fl avor to food. Jewelry can also be composed of minerals, such as gold, turquoise, and diamonds. Tell students to pay close attention to the video to learn more about minerals, their characteristics, how they are formed, and their everyday uses.


Video Script 1. What do copper wire,… 2. …talcum powder,… 3. …jewelry,… 4. …and table salt have in common? 5. All these things are made from minerals. 6. So, what exactly are minerals? 7. What’s the difference between a rock and a mineral? 8. What are some of the characteristics of minerals? 9. And how do you go about identifying them?10. During the next few minutes, we are going to answer these questions and

others,…11. …as we explore the fascinating topic of minerals.12. Graphic Transition - What are Minerals?13. The mineral turquoise, in this piece of jewelry,… 14. …and the mineral gypsum, used to make sheetrock, are just two examples of

the more than 3,000 known minerals.15. Surprisingly, though, over 90% of the rocks in the Earth’s crust are comprised of

only 20 minerals. These minerals are generally called rock-forming minerals.16. Chances are, the rocks you see around your neighborhood are made up of two

or more of these common rock-forming minerals. 17. For example, this rock, called granite, contains three main minerals: feldspar;

quartz; and black mica, or biotite.18. So, what exactly is a mineral?19. A mineral is a naturally occurring solid that has a defi nite chemical makeup and

crystal shape.20. Phew! That’s a mouthful! So, let’s break this defi nition down into smaller pieces.21. To start with, minerals are found in nature.22. Minerals are also solids with a defi nite volume and shape.23. And minerals have a crystal structure. A crystal is made of particles which form

a pattern that repeats itself over and over.24. Sometimes a crystal pattern is quite obvious, as is the case with this quartz

crystal.25. But sometimes special microscopes are needed to observe crystal shapes.26. Another characteristic of minerals is that they have a defi nite chemical makeup,

which means they contain specifi c combinations of elements.27. You can think of an element as a chemically-pure substance, like iron.28. Most minerals are made up of two or more elements. Quartz, for example, is

made up of the elements silicon and oxygen.29. Graphic Transition - Grouping Minerals30. As we mentioned, there are thousands of different kinds of minerals.31. Geologists often classify them in groups to make them easier to study.


Video Script32. A common way to group minerals is based on their chemical makeup.33. For example, minerals are often placed into two main groups: silicate minerals

and non-silicate minerals.34. Silicon, the element in silicate minerals, is very common in rocks.35. Quartz and feldspar are examples of silicate minerals.36. Non-silicate minerals do not contain silicon.37. Sulfur, calcite, and salt are examples of non-silicates.38. Sometimes scientists group minerals as metallic…39. ...or non-metallic.40. Galena and copper are examples of metallic minerals,…41. ...whereas halite and calcite are non-metallic minerals.42. Graphic Transition - Identifying Minerals43. Because there are so many different kinds of minerals, it isn’t always easy to tell

them apart.44. You Compare! Which of these two minerals is gold?45. The one on the left is gold. The one on the right looks like gold but is called pyrite,

or “fool’s gold.”46. Even though these minerals look similar, they have characteristics which make

them different from one another.47. Each mineral has its own specifi c properties that can be used to identify it.48. A property is a characteristic of a mineral.49. One of the easiest mineral properties to notice is the color of a mineral’s outer

surface.50. The problem with color, however, is that the same mineral can come in several

different colors.51. And in some cases, different minerals may have the same color, as we just saw

with pyrite and gold.52. Sometimes a mineral’s streak is helpful in identifying it. Streak is the color of a

minerals’ powder when rubbed against a piece of porcelain. 53. Notice how this mineral has a shiny metallic appearance,…54. ...but this mineral has a dull appearance. This property is referred to as luster.55. Luster is the way the surface of a mineral refl ects light. There are many ways that

minerals refl ect light.56. Metallic, nonmetallic, waxy, and earthy are some of the ways we describe a

mineral’s luster.57. You Observe! Was this mineral scratched with a fi ngernail or with a steel knife? 58. Your fi ngernail can’t scratch it, but a steel knife can.59. This softer mineral, however, called talc, can easily be scratched with a fi ngernail.60. Different minerals have varying degrees of hardness.61. To determine the hardness of minerals, scientists use a scale called Mohs hardness

scale.


Video Script62. On this scale, talc is the softest mineral at 1 and diamond is the hardest at 10.

Between these two extremes are other minerals with progressing degrees of hardness.

63. Different types of minerals tend to break in different ways as well.64. Notice how this piece of halite…66. ...and this piece of biotite break along fl at planes.67. You Observe! Describe how this quartz breaks.68. Quartz breaks unevenly.69. Fracture is the tendency of minerals to break along irregular or curved surfaces.70. Another way minerals differ is in the types of crystal structures that they form.71. There are several different basic crystal shapes.72. In some cases, minerals can be identifi ed by other properties, such as density,

taste, and odor, to name just a few.73. Graphic Transition - How Do Minerals Form?74. Minerals form in a variety of ways. 75. Many minerals are formed from molten rock beneath or above Earth’s surface.76. When molten rock cools, mineral crystals are formed.77. Mica, feldspar, magnetite, and quartz are formed when molten rock cools.78. Changes in temperature, pressure, or chemical makeup inside Earth can also alter

rocks to form different minerals.79. Garnet, graphite, talc, and magnetite are formed this way.80. Sometimes minerals form in solutions of mineral-rich water. 81. These formations were formed in Mono Lake, California when the lake was much

deeper.82. Minerals such as sulfur and iron are often formed in geothermal pools.83. Sometimes, when mineral-rich water evaporates, it leaves behind mineral crystals.84. These salt crystals in Death Valley were formed when salt-rich water evaporated.85. These are just a few examples of how minerals form.86. Graphic Transition - Summing Up87. During the past few minutes, we’ve explored some of the fascinating

characteristics of minerals.88. We saw that minerals are very important substances which make up rocks.89. Minerals are naturally occurring, inorganic solids that have a defi nite crystal shape

and a defi nite chemical composition. 90. We discussed how geologists sometimes classify minerals as silicates or non-

silicates.91. Minerals possess many different properties, which can be used to identify them. 92. We briefl y investigated the properties of color,…93. ...streak,…94. ...and luster.95. We also explored the properties of hardness and the use of Mohs hardness scale.


Video Script 96. Some of the other properties used in identifying minerals were demonstrated,

including cleavage, fracture, and crystal shape. 97. So, the next time you use something made from minerals,… 98. ...or notice a nice piece of jewelry,… 99. ...think about some of the things we’ve just discussed.100. You just might think about minerals a little differently.Graphic Transition - Video AssessmentFill in the correct word to complete the sentence. Good luck and let’s get started.1. ________ have a defi nite chemical makeup and crystal shape.2. A ______ is a characteristic of a mineral.3. This mineral has a metallic _______.4. ________ is the tendency of minerals to break along fl at surfaces.5. When ________ rock cools, mineral crystals form.

Answers can be found on page 12


Answer Key to Student AssessmentsPre-Test (p. 14-15) Post-Test (p. 16-17)

Video Review (p. 18)

1. d - minerals 2. c - elements 3. b - silicon 4. a - properties 5. c - luster 6. d - Mohs hardness scale 7. a - fracture 8. d - molten rock 9. b - streak10. d - crystal11. true12. true13. true14. false15. false16. Properties used to identify minerals include color, hardness, streak, luster, cleavage, fracture, crystal shapes, density, taste, and odor.17. Cleavage is the tendency of minerals to break along fl at surfaces. Fracture is the tendency of minerals to break along irregular or curved surfaces.18. Rocks are made up of a mixture of two or more minerals.19. Mineral crystals form when molten rock cools.20. An element is a chemically pure substance. A mineral is made of two or more elements.

1. The mineral on the left is gold. The mineral on the right is pyrite, or fool’s gold. 2. The mineral could not be scratched with a fi ngernail, but it was scratched with a steel knife.3. Quartz breaks unevenly.

1. minerals2. property3. luster4. cleavage5. molten

1. a - fracture 2. b - streak 3. d - Mohs hardness scale 4. d - molten rock 5. d - minerals 6. b - silicon 7. d - crystal 8. a - properties 9. c - elements10. c - luster11. false12. true13. false14. true15. true16. Rocks are made up of a mixture of two or more minerals.17. An element is a chemically pure substance. A mineral is made of two or more elements.18. Mineral crystals form when molten rock cools.19. Cleavage is the tendency of minerals to break along fl at surfaces. Fracture is the tendency of minerals to break along irregular or curved surfaces.20. Properties used to identify minerals include color, hardness, streak, luster, cleavage, fracture, crystal shapes, density, taste, and odor.


In Your Own Words (p. 20)

Writing Activity (p. 20)

Vocabulary (p. 19 )Answer Key to Student Activities

1. Minerals are found in nature and have a defi nite chemical makeup and crystal shape. 2. Minerals form when molten rock on or beneath Earth’s surface cools and when mineral-rich water evaporates. They can also form as a result of changes in temperature, pressure, and chemical makeup of rocks.3. Luster refers to the way a mineral’s surface refl ects light. Metallic, nonmetallic, waxy, and earthy are all terms used to describe luster.

1. mineral2. crystal3. fracture4. element5. silicon6. properties7. streak8. luster9. Mohs hardness scale10. cleavage

Making Crystals (p. 22)1. Evaporation causes crystals to form from the salt solution. This is similar to the process by which sulfur and iron minerals are formed when water evaporates from geothermal pools, and when salt crystals form in shallow pools. 2. The crystals form when the sugar solution cools. This is similar to the process by which molten rock cools to form mineral crystals.3. The sides and bottom of the pan are the sites of formation in the salt solution. In the sugar solution, the crystals form on the string or sides of the test tube.

Mineral Identifi cation (p. 24)1. Answers will vary.2. Answers will vary.3. Density, crystal structure, magnetism, and odor are other properties that can be used to identify minerals.

Exploring Mono Lake (p. 25)1. Mono Lake is two to three times saltier than the ocean because there is no outlet for the mineral-rich water. Fresh water evaporates, leaving behind the minerals and salts. 2. Tufa towers form when the lake water, saturated with minerals and salts left behind by evaporation, comes in contact with fresh water.3. Mono Lake brine shrimp, alkali fl ies, and hundreds of species of migratory birds, including the California gull, live in and around Mono Lake. Fish are not able to survive in the lake.4. The water level dropped drastically when Los Angeles began diverting water, forcing many of the organisms living around the lake to leave the area.

A mineral is a naturally occurring solid that has a defi nite chemical makeup and crystal shape. Minerals contain specifi c combinations of elements, which are chemically pure substances. Minerals are identifi ed based on their properties, or characteristics. For example, minerals can be identifi ed by the color of their outer surface. Minerals can also be identifi ed by their streak, which is the color of the mark they leave when rubbed on a piece of porcelain. Luster, or the way the surface of a mineral refl ects light, is another property. Metallic, nonmetallic, waxy, and earthy are some words used to describe a mineral’s luster. A mineral’s hardness can be determined by using Mohs hardness scale. Cleavage refers to a mineral’s tendency to break along fl at planes. Fracture is the tendency of minerals to break along irregular or curved surfaces.

Pre-Test

4. These are physical characteristics used to identify minerals:

5. Metallic, nonmetallic, waxy, and earthy are some terms used to describe this property:

1. Rocks are made of a mixture of two or more of the following:

2. Most minerals are made up of two or more chemically pure substances called:

3. Silicate minerals contain this element, which is very common in rocks:

Circle the best answer for each of the following questions.

6. Scientists use this to help determine the hardness of minerals:

10. A solid made up of particles that form repeating patterns:

7. This refers to the tendency of quartz and other minerals to break along irregular or curved surfaces:

8. This material must cool in order for mineral crystals to form on or beneath Earth’s surface:

9. The color of a mineral’s powder when rubbed against a porcelain plate is called:

a. igneous b. sedimentary c. diamonds d. minerals

a. rocks b. nonsilicates c. elements d. silicates

a. halite b. silicon c. graphite d. quartz

a. hardness b. color b. color b. color c. luster c. luster c. luster d. streak

a. properties b. traits c. genes d. linkages

a. hammer a. hammer a. hammer b. microscope c. telescope d. Mohs hardness scale

a. fracture b. cleavage c. strata d. shale

a. wax b. water b. water b. water c. geysers d. molten rock

a. luster a. luster a. luster b. streak c. pressure d. precipitation

a. rock b. element c. igneous rock d. crystal

Visual Learning Company

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14Minerals

Name

Write a short answer for each of the following.

Pre-Test

16. List three different properties used to identify minerals.

17. Differentiate between cleavage and fracture.

18. Of what are rocks made?

11.

12.

13.

14.

15.

Write true or false next to each statement.

19. How do minerals form from molten rock?

20. What is the difference between an element and a mineral?

Minerals are found in nature.

Rocks are made up of a mixture of two or more minerals.

Approximately twenty of 3,000 minerals make up over 90% of all rocks.

Luster is the color of a mineral’s powder when rubbed against a piece of porcelain.

Diamond is a 10 on Mohs hardness scale, which means that it is very soft.


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15Minerals

Name

Circle the best answer for each of the following questions.

Post-Test

4. This material must cool in order for mineral crystals to form on or beneath Earth’s surface:

5. Rocks are made of a mixture of two or more of the following:

1. This refers to the tendency of quartz and other minerals to break along irregular or curved surfaces:

2. The color of a mineral’s powder when rubbed against a porcelain plate is called:

3. Scientists use this to help determine the hardness of minerals:

6. Silicate minerals contain this element, which is very common in rocks:

10. Metallic, nonmetallic, waxy, and earthy are some terms used to describe this property:

7. A solid made up of particles that form repeating patterns:

8. These are physical characteristics used to identify minerals:

9. Most minerals are made up of two or more chemically pure substances called:

a. fracture b. cleavage c. strata d. shale

a. luster a. luster a. luster b. streak c. pressure d. precipitation

a. hammer a. hammer a. hammer b. microscope c. telescope d. Mohs hardness scale

a. wax b. water b. water b. water c. geysers d. molten rock

a. igneous b. sedimentary c. diamonds d. minerals

a. halite b. silicon c. graphite d. quartz

a. rock b. element c. igneous rock d. crystal

a. properties b. traits c. genes d. linkages

a. rocks b. nonsilicates c. elements d. silicates

a. hardness b. color b. color b. color c. luster c. luster c. luster d. streak


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Post-Test

Write a short answer for each of the following.

16. Of what are rocks made?

17. What is the difference between an element and a mineral?

18. How do minerals form from molten rock?

11.

12.

13.

14.

15.

Write true or false next to each statement.

19. Differentiate between cleavage and fracture.

20. List three different properties used to identify minerals.

Luster is the color of a mineral’s powder when rubbed against a piece of porcelain.

Approximately twenty of 3,000 minerals make up over 90% of all rocks.

Diamond is a 10 on Mohs hardness scale, which means that it is very soft.

Minerals are found in nature.

Rocks are made up of a mixture of two or more minerals.


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Name

1. Which of these two minerals is gold?

3. This mineral has a metallic ___________.

2. A ___________ is a characteristic of a mineral.

1. ___________ have a defi nite chemical makeup and crystal shape.

4. ___________ is the tendency of minerals to break along fl at surfaces.

5. When ___________ rock cools, mineral crystals form.

After you watch the video, test your knowledge with these questions.

While you watch the video, answer these questions:

2. Was this mineral scratched with a fi ngernail or with a steel knife?

3. Describe how this quartz breaks.

Video Review

You Observe!

You Observe!

You Compare!


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The color of a mineral’s powder when rubbed against a piece of porcelain.

A chemically pure substance.

Vocabulary

Scientists use this to determine a mineral’s hardness.

Use these words to fi ll in the blanks next to the sentences below.

A solid made of particles that form a repeating pattern.

The tendency of minerals to break along irregular or curved surfaces.

This describes the way a mineral’s surface refl ects light.

Physical characteristics used to identify minerals.

1.

7.

2.

6.

8.

4.

5.

3.

The element in silicate minerals that is found in many rocks.

9.

The tendency of a mineral to break along fl at surfaces.10.

Wo

rds

A naturally occurring solid that has a defi nite chemical makeup and crystal shape.

luster properties Mohs hardness scale fracture mineralcleavage crystal silicon streak element


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2. Describe two ways that minerals form.

1. List three characteristics of minerals.

Use the correct word from above to complete the sentences in the following paragraph.

Writing Activity

A __________ is a naturally occurring solid that has a defi nite chemical makeup

and crystal shape. Minerals contain specifi c combinations of __________, which

are chemically pure substances. Minerals are identifi ed based on their

__________, or characteristics. For example, minerals can be identifi ed by the

__________ of their outer surface. Minerals can also be identifi ed by their

__________, which is the color of the mark they leave when rubbed on a piece

of porcelain. Luster, or the way the surface of a mineral refl ects __________, is

another property. Metallic, nonmetallic, waxy, and earthy are some words used

to describe a mineral’s __________. A mineral’s __________ can be determined

by using Mohs hardness scale. __________ refers to a mineral’s tendency to

break along fl at planes. __________ is the tendency of minerals to break along __________ is the tendency of minerals to break along __________

irregular or curved surfaces.

In Your Own Words

3. What is a mineral’s luster and what are common words used to describe it?

Wo

rds fracturefracture lightlight color color mineral mineral propertiesproperties cleavage elements streak hardness luster


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Making CrystalsBackground: A mineral is a naturally occurring solid with a defi nite chemical makeup and crystal structure. A crystal is made of particles that form a repeating pattern. Some mineral crystals form when molten rock cools on or below Earth’s surface. Mineral crystals can also form in mineral-rich solution or when mineral-rich water evaporates. In this activity you will make your own crystals.

Materials:test tubetest tube racksugarsaltwateroven mitttwo glass jars

small potshallow glass panhot platetoothpickstringmagnifying lensaluminum foil

Activity:1. Before you begin, draw pictures of a salt crystal and sugar crystal on the following page. Use the magnifying lens to closely examine the crystals. 2. To create the salt solution, add salt to a glass jar that is half full of water, stirring constantly. Continue adding the salt until it stops dissolving in the water.3. Pour a thin layer of the salt solution into the glass pan and set aside.4. To create the sugar solution, repeat step 2, substituting sugar for salt.5. Your teacher will pour the sugar solution into the small pot and heat it on the hot plate, stirring frequently. Once the solution is heated, your teacher will transfer the liquid into the test tube, which is suspended from the test tube rack. Caution: The sugar solution is very hot! Do not touch the test tube once the liquid has been poured into it. If you need to touch it, make sure your hands are protected with an oven mitt.6. Tie one end of the string to the center of the toothpick. Place the toothpick over the top of the test tube, allowing the string to dangle into the solution. You do not want the string to touch the bottom or sides of the test tube, so adjust as needed.7. Lightly cover the test tube with aluminum foil and set aside. 8. Do not touch the two solutions for one week. At the end of one week, observe the pan and test tube. Draw pictures of the crystals formed from the salt and sugar solutions on the following page. Use a magnifying lens if necessary. 9. Answer the questions on the following page.


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Making Crystals

Salt crystal Sugar crystal

Salt crystal - one week later Sugar crystal - one week later

Questions:1. What process caused the salt solution to form crystals? Give an example of how this occurs in nature.

2. What process caused the sugar solution to produce crystals? Give an example of how this occurs in nature.

3. Crystals need a site for formation. Identify the sites for the sugar and salt solutions.


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Mineral Identifi cationBackground: Minerals possess a set of specifi c properties, or characteristics, that can be used to help identify them. Color is one of the most obvious properties, yet it can also be the least helpful in identifying materials. Color is often determined by Color is often determined by Colorslight variations in a mineral’s chemical formula. One mineral can often come in many different colors, and two minerals can have the same color. A mineral’s hardnesscan be determined by a scratch test. Mohs scale of hardness ranks minerals from 1 (softest) to 10 (hardest). Minerals are also identifi ed based on how they break. Cleavage refers to a mineral’s tendency to break along fl at surfaces. Fracture refers to a mineral’s tendency to break along irregular or curved surfaces. A mineral’s streak refers to the color powder it leaves when rubbed against a piece of porcelain. Minerals can also be identifi ed based on their luster, which is the way the surface of a mineral refl ects light. Metallic, nonmetallic, waxy, earthy, glossy, and dull are common terms used to describe luster. These are just a few examples of properties that can be used to identify minerals.

Materials:5 numbered samples of unknown mineralscopper pennyglass squaresteel fi le or nailporcelain streak platemagnifying lensmineral identifi cation key

Activity:Record your observations in the chart on the following page.1. Identify the color and luster of each mineral.2. Rub each mineral against the streak plate and record the color of the streak.3. Use a penny, glass square, steel nail or fi le, and your fi ngernail to try to scratch the mineral. Refer to the table on the following page to determine the approximate hardness of the mineral.4. Observe the surface of each mineral to determine if it displays cleavage or fracture.5. Your teacher will provide you with the names and descriptions of the unknown minerals, but will not indicate to which sample they belong. Match your unknown samples with the correct mineral name and description.


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23Minerals

Name

Mineral Identifi cation

Sample # Color and luster

Hardness Cleavage or fracture

Streak Mineral name

The following table, based on Mohs scale of hardness, can be used to approximate a mineral’s hardness:

Questions:1. Which property do you feel was the most helpful in identifying the minerals? Why?

2. Which property do you feel was the least helpful in identifying the minerals? Why?

3. What other properties do you think could be helpful in identifying minerals?

Material Hardnessfi ngernail 2.5coin 3.5glass 5.5steel knife 6.5

*For example, if a mineral can be scratched by a coin, but not a piece of glass, it has a hardness between 3.5 and 5.5.


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Exploring Mono LakeActivity: Read the information below and answer the questions that follow.

Mono Lake is a large, ancient lake located in the Great Basin Desert in eastern California, near the Nevada border. It covers about 60 square miles (155 km2) and is 13 miles (20.9 km) wide by 8 miles (12.9 km) long. It is believed to be about 760,000 years old, making it one of the oldest lakes in North America. It is a closed hydrological basin, which means that water fl ows in, but does not fl ow out. Since its formation, minerals and salts from the surrounding area have been carried into the lake by rivers and streams that feed into it. Fresh water is able to leave the lake via evaporation, which is the process through which water becomes gas. However, the minerals and salts do not evaporate, causing them to remain in the lake. As a result, the lake is two to three times as salty as seawater. The mineral-rich water is denser than ocean water and will help you fl oat if you swim in it!

One of the most remarkable features of Mono Lake are its tufa towers. Tufa is a type of limestone rock, which contains the mineral calcite. Some of the tufa towers located around the lake are estimated to be between 200 and 900 years old. Tufa towers form when freshwater comes in contact with the salty water of Mono Lake. The towers form underwater at the mouth of the streams. They become visible as lake water evaporates and the lake level drops. Some tufa towers, as old as 13,000 years, are located beyond the current edges of the lake, illustrating the outer boundaries of the lake.

Due to the high salinity of the water, there are no fi sh native to the lake and efforts to introduce fi sh have failed. However, the lake is home to trillions of Mono Lake brine shrimp, which are tiny shrimp that exist nowhere else in the world. They offer no nutritional value to people, but do feed the birds that inhabit the area. The lake is also inhabited by alkali fl ies, which, in addition to the brine shrimp, attract approximately 100 species of migratory birds to the area. Mono Lake has the second largest population of California gulls, with over 44,000 to 65,000 living at the lake periodically throughout the year.

In the early 1940s, the fast-growing city of Los Angeles needed more water than was available in southern California. In search of water, the city turned to Mono Lake and began diverting water that naturally fed into the lake. This caused the lake level to drop quickly. Soon more water was evaporating than entering the lake, causing the lake level to drop drastically. This forced many animals to leave the area. In the 1970s, the Mono Lake Committee and the Audubon Society fi led a famous law suit to protect the lake, and in 1994 the California State Water Resources Control Board granted the lake special protections. Since that time, the lake level has risen slowly.

Questions:1. What makes the water of Mono Lake unique? Why is it this way?2. How do tufa towers form?3. What organisms live in and around Mono Lake? What organisms are not able to survive?4. What happened to Mono Lake when Los Angeles began diverting water?


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25Minerals

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minerals · elements, which are chemically pure substances. different minerals combine to form...

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