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Content Benchmark E.8.C.6
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Students know minerals have different properties and different distributions according to how they form. E/S

If it can’t be grown, it has to be mined is the slogan for the Mineral Information Institute, an organization which provides information and materials to teachers and students that result in an understanding that mineral and energy resources are essential to society and are produced in an environmentally and socially responsible manner (accessed at Everything we use in our daily life originates from our natural resources. Often students’ associate minerals with vitamins, but to a geologist the meaning of the word mineral is quite different. By definition, a mineral is a naturally formed, inorganic solid having a specific chemical composition and characteristic crystal structure.

Variety of Minerals
There are approximately 4000 varieties of minerals which can be classified into one of eight major mineral classes similar to how biologists classify living organisms into groups such as plants, animals, fungi, and bacteria.

Interactive Chart of Minerals
click on any underlined link to see a sample of the mineral.
Silicate Oxide Carbonate Sulfide Sulfate Halide Hydroxide Phosphate Native Element
tourmaline magnetite siderite pyrite barite fluorite limonite apatite graphite
staurolite hematite malachite galena anhydrite halite     sulpher
garnet corundum azurite chalcopyrite gypsum       
olivine bauxite dolomite sphalerite          
augite   calcite            

Figure 1. Interactive Chart of Minerals.

Mineral Classification
Minerals, however, are classified into groups by their composition and crystal structure. Ninety five percent of the rocks found in Earth’s crust contain minerals known as silicates. Silicates are the most abundant minerals and make up about 25% of all known minerals. The structure of all silicates is based on a silicon atom surrounded by four oxygen atoms. Silicates can be further classified into six subclasses differentiated by their structure. Common silicates include quartz, feldspars, pyroxene and olivine.

Figure 2Common Silicate minerals.

Three fourths (75%) of known minerals are non-silicates. These remaining minerals are grouped mainly by their chemical composition. Minerals formed when metals, like iron and aluminum, bond with oxygen are known as oxides such as hematite, corundum, magnetite, and rutile. Many oxides form by the weathering of other minerals. Corundum (AlO2) is best known for its gem forms: ruby and sapphire.

Figure 3. Common Oxide mineral samples..
(From h

Sulfides also contain metals, but instead of oxygen, they combine with one or two sulfur atoms. The most abundant sulfide in Earth’s crust is pyrite, also known as “fool’s gold.”

Figure 4. GIron Pyrite sample

Compared to a sample of crystalline gold (Figure 5) it is easy to see why pyrite (Figure 4) has “fooled” many people into thinking they have “struck it rich” when in actuality they have found a mineral of little value.

Figure 5. Crystalline gold sample.

Sulfides include many ores which can occur in large deposits with economic value. Ores are rocks that contain enough metal or valuable minerals to make them worth mining. The concentration of metal determines its value. Ores containing iron, such as galena, must contain more than 50% to be economically valuable, whereas ores containing silver or platinum may only require 0.01% in order to be valuable. Other common sulfides are sphalerite, a zinc ore, and chalcopyrite, an ore containing both copper and iron.

Another group of non-silicate minerals are the halides. Table salt, sodium chloride (NaCl), is the most common halide, known as Halite. Halides dissolve easily in water and are often soft and transparent.

Figure 6. Halide Mineral Sample of Fluorite (CaF2).
(From ery/fluorite-detail08.jpg)

Carbonates, Phosphates, and Sulfates make up the remaining mineral groups composed of chemical compounds. Despite what their name implies Phosphates may or may not contain phosphorus. Regardless of their name, some contain arsenic, vanadium, or antimony. Similarly, sulfates do not all contain sulfur. They can contain chromium, tungsten, selenium, or molybdenum. Common sulfates include gypsum, barite, and anhydrite.

Figure 7.Gypsum Starburst, a common sulfate mineral, in a not so common form.

Carbonates are the most extensive group aside from silicates and phosphates. They are minerals consisting of metals and the carbonate (CO3)2- ion. These minerals are further classified by their crystal structure into calcite, aragonite, and dolomite. Calcite is the most abundant carbonate mineral.

Figure 8. Calcite and Dolomite two common carbonate minerals.

Although most minerals are formed by chemicals combined in various compounds, others exist simply as elements in their pure form. These minerals are called native elements and are made up entirely of the same types of atoms. Copper, gold, lead, nickel, iron, and diamonds are all examples of the elemental form of minerals.

Figure 9. Pure gold sample.

Figure 10. A sample of pure copper.

Mineral Identification
With all these thousands of minerals, how can geologist tell them apart? There are simplified methods of identification that can be done in the field using simple equipment like a rock hammer, scale and/or a hand-lens. Other identification methods are more elaborate and are commonly done in a laboratory setting utilizing high powered microscopes or chemical analysis. Just as you can typically spot your best friend in a crowd of people, often times a geologist can identify a mineral simply by looking at the sample. Sometimes, however, it is easier to identify an individual if it they are separated from the group. Geologist can separate a mineral from the rock it is found in by using their rock hammer, as they do so they note how the mineral breaks apart. Different minerals have different breakage patterns the pattern or way the mineral breaks in known as cleavage. Mica, for example, tends to break neatly into thin sheets, whereas a mineral with poor cleavage, like quartz, may break into jagged/angular pieces.

Attempting to scratch the mineral sample with the nail or even another known mineral can also provide clues to the identifying factor known as hardness. Friedrich Mohs invented his famous scale for determining mineral hardness back in 1822, when asked to organize the mineral collection of a wealthy Austrian banker. The scale ranks minerals from 1 the softest (talc) to 10 the hardest (diamond).

Figure 11. Mohs Hardness Scale showing minerals at each hardness level.

Crystal Structure
Upon close inspection, the shape of the individual mineral crystals may be noted. Crystals form patterns and each mineral type possesses its own specific pattern. There are seven crystalline systems that can be used to help identify a mineral sample: cubic, tetragonal, rhombic, trigonal, hexagonal, monoclinic and triclinic.

Figure 12. Crystal Structures Diagram

The crystalline structure can help identify the mineral, but not necessarily the element itself. For example, the element carbon can be found as both diamond and graphite.

Figure 13. Diamond and Graphite comparison. Although both are made from pure carbon, one is the hardest substance known to man the other is one of the softest.

Density of the sample can also be used as an identifying factor. By finding the displaced volume and mass of an unknown sample, the density (D = M/V) can be calculated. This ratio, known as specific gravity, can be compared to complied tables containing values for known minerals to assist in identification.

Fracture, sometimes with pairing virteous to adamantine transparent, translusent sometimes has hexagonal crystals 4.02 CORUNDUM
Fracture virteous transparent to opaque sometimes striations 3.02-3.2 TOURMALINE
Fracture virteous to resinous transparent to opaque sometimes isometric crystals 3.5-4.3 GARNET
Conchoidal Fracture virteous to greasy transparent to translusent sometimes has hexagonal crystals 2.65 QUARTZ
Conchoidal Fracture virteous transparent to translusent frequently as granular masses 3.27-4.27 OLVINE
Fracture, dull opaque sometimes oolitic or magnetic 5.26 HEMATITE
Fracture dull translusent, opaque earthy color and apperance 2.7-4.3 LIMONITE
Fracture dull earthy translusent, opaque pisolitic 2.00-2.55 BAUXITE
Mineralogy / Petrology (1997) By: Art Crossman

Figure 14. Sample Mineral Identification Chart, Including Specific Gravity

Color can also be used as an identifying characteristic, but it is often unreliable due to impurities or weathering. Quartz, for example, can be found in its pure state as clear and colorless, but it can also be found in various colors ranging from violet, pink, green, and even black.

Figure 15.Various Quartz Samples.

A more reliable test utilizing color is the streak test. This can be performed by scratching a mineral against a rough unglazed piece of ceramic or porcelain tile. The color of the powder or streak remaining on the plate is typically the same for all samples of a specific mineral. It can also be used to tell two similarly looking samples apart. Gold and pyrite are both golden color minerals, but their streak immediately distinguishes them. Gold produces a golden streak, but pyrite produces a dark green-black streak. Galena and hematite can also be easily confused because of their similar dull gray color. When tested on a streak plate galena reveals the same dull gray color, but hematite produces a clearly identifiable blood-red streak.

Figure 16.Streak plate comparison of hematite and pyrite.

Geologist may also observe the sample’s luster – the way the mineral reflects and refracts light. Typically luster is described as metallic or non-metallic. Non-metallic lusters can be further described as greasy, shinny, glassy, or earthy.

Figure 18.Examples of the various types of mineral luster.

How Minerals Form
There are two main ways in which minerals form; either by the crystallization of materials dissolved in water or through crystallization of melted materials. The easiest way for crystals to develop is through the evaporation of water. For example, halite, gypsum, and calcite can all form from the evaporation of seawater. The crystal size depends on the rate of evaporation, with large crystals resulting from slow evaporation, whereas, quick evaporation leads to smaller crystals.

Figure 19.The Bonneville Salt Flats of Utah contain halite formed by evaporation

In addition to seawater, elements that form minerals can also dissolve in hot water that is often found near magma instructions, and form a solution. When this hot solution cools, the elements and compounds crystallize and form new minerals. Pure metals that crystallize underground often form narrow channels or slabs of minerals known as veins. These veins often contain valuable ores such as hematite, gold, silver, and galena

When molten rock cools, atoms also bond together into mineral crystals. Minerals form as hot magma cools inside the crust or when lava hardens on the Earth’s surface. The size of the crystals depends on the rate of cooling. Slow cooling leads to large crystals. Magma closer to the surface loses heat energy much faster than magma that hardens deep below the ground, therefore, the lava cools quickly and smaller crystals result

Bowen’s Reaction Series

Figure 20.Bowen’s Reaction series shows minerals formation at various temperatures

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Content Benchmark E.8.C.6

Students know minerals have different properties and different distributions according to how they form. E/S

Common misconceptions associated with this benchmark

1. Students have difficulty understanding the definition of a mineral.

Students often believe rocks and minerals are the same thing. They believe humans can fabricate rocks and minerals. In addition, they believe minerals are not important to their lives.

For more information about these misconceptions and for strategies to address them, visit the Common Misconceptions about Rocks and Minerals website at

What Is It? An interactive activity can be used to assess prior knowledge can be accessed at

What Is It? Directions and answer key is found at

2. The Source of Student Misconceptions about Rock Formation

In depth research article that analyzes narrative essays - stories of rock formation - written by pre-service elementary school teachers.


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Content Benchmark E.8.C.6

Students know minerals have different properties and different distributions according to how they form.  E/S

Sample Test Questions

1st Item Specification: Understand the properties of minerals (e.g. color, luster, hardness, reactivity, light transmission, and density).

Depth of Knowledge Level 1

  1. Which property describes the reflection of light off the surface of the mineral?
    1. Color
    2. Luster
    3. Density
    4. Hardness
  1. Which scale can be used to measure how resistant a mineral is to scratching?
    1. Mohs scale
    2. Fujita scale
    3. Richter scale
    4. Saffir-Simpson scale
  1. Which property is the LEAST reliable for mineral identification?
    1. Luster
    2. Streak
    3. Color
    4. Hardness
  1. Which of the following minerals has a nonmetallic luster?
    1. Gold
    2. Pyrite
    3. Quartz
    4. Graphite
  1. A mineral was found that has a metallic luster and is gold in color.  Which property could NOT be used to determine if the sample is gold or pyrite?
    1. Color
    2. Streak
    3. Density
    4. Hardness

Depth of Knowledge Level 2

  1. Use Mohs Scale of Hardness to answer the question.

Mohs Scale.JPG

  1. Which mineral would be weathered the MOST after being placed in a rock tumbler for fifteen minutes?
    1. Gypsum
    2. Fluorite
    3. Topaz
    4. Diamond
  1. Use the chart to answer the following question.


  1. Which mineral has a different color in its powdered form than its original form?
    1. Graphite
    2. Kaolinite
    3. Magnetite
    4. Pyrite

2nd Item Specification: Understand how minerals form and where they are typically found.

Depth of Knowledge Level 1

  1. The most likely way for a crystal to form is by
    1. boiling.
    2. evaporation.
    3. condensation.
    4. sublimation.
  1. Minerals are found
    1. as liquids.
    2. in all rock types.
    3. only as native elements.
    4. as renewable natural resources.
  1. In the desert, water evaporates and leaves deposits of salt crystals. These crystals are known as
    1. talc and calcite.
    2. quartz and topaz.
    3. gypsum and halite.
    4. fluorite and apatite.
  1. The range of chemical composition in a mineral typically results from
    1. time and place of origin.
    2. change in atomic structure.
    3. changes in physical properties.
    4. inclusions of other mineral grains.

Depth of Knowledge Level 2

  1. Hematite is a mineral that forms during the weathering of iron-bearing minerals. It is essentially rusted; therefore, what must be present in order for hematite to form?
    1. Magma
    2. Salt
    3. Lava
    4. Water
  1. Use the diagram to answer the following question.


  1. Which diagram shows the formation of minerals with the relatively largest crystal size?
    1. Diagram C as there is almost the same amount of lava and magma in the diagram.
    2. Diagram B because magma takes a longer amount of time to cool than lava.
    3. Diagram B as magma has a shorter cooling time than lava.
    4. Diagram A because the mineral solution is above the magma.

Constructed Response E.8.C.6

1. The data table below shows the color, luster, and streak of five unidentified mineral samples.

  1. Which mineral samples have different color in its powdered from than its original form?
  2. Explain how you could determine the relative hardness of each mineral sample.
  3. What tools would a field geologist need to take on a job that would require fluorite, calcite, quartz, and gypsum to be distinguished?  Explain why is each of these tools is necessary and important.

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Content Benchmark E.8.C.6

Students know minerals have different properties and different distributions according to
how they form. E/S

Answers to Sample Test Questions

  1. B, DOK Level 1
  2. A, DOK Level 1
  3. C, DOK Level 1
  4. C, DOK Level 1
  5. A, DOK Level 1
  6. A, DOK Level 2
  7. D, DOK Level 2
  8. B, DOK Level 1
  9. B, DOK Level 1
  10. C, DOK Level 1
  11. A, DOK Level 1
  12. D, DOK Level 2
  13. B, DOK Level 2

Constructed Response 3 Point Answer and Score Rubric:

3 points

Response addresses all parts of the question clearly and correctly.
Mineral sample A, C, or D has a different color than its streak. 
Much in the same way that Mohs hardness scale was developed, two unknown samples could be rubbed against each other to see which sample scratches the other. The harder sample will scratch the softer sample. For instance, if Sample B scratches Sample A, then you know that Sample A is softer than Sample B. If Sample C and Sample A are rubbed together and Sample C scratches Sample A, then you know that Samples B and Sample C are harder than Sample A. Continue the process comparing two samples at a time to create an ordered relative hardness for the samples.
A geologist would have to bring a piece of unglazed porcelain to use as a streak plate, a kit to test hardness including a glass plate and a steel blade, a rock hammer to check the fracture and cleavage and safety goggles.  These tools are important because all samples could be found to have the same color, so the samples could not be identified solely by color. The samples have differing hardness, cleavage/fracture and streak (all have the same color streak, however if the fluorite or calcite samples are found in a different color, the streak will confirm the identification).  Once the other properties are determined, then identification could be confirmed.

2 points

Response addresses all parts of the question and includes only minor errors.

1 point

Response does not address all parts of the question.

0 points

Response is totally incorrect or no response was provided. 

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Content Benchmark E.8.C.6

Students know minerals have different properties and different distributions according to how they form. E/S

Intervention Strategies and Resources

The following is a list of intervention strategies and resources that will facilitate student understanding of this benchmark.

1. The Mineral Information Institute – free teaching materials.

MII site resource that contains packets to download or a form to fill in and receive information by mail. Here you will find Everyday Uses of Minerals, the Every American Born Will Need Poster, along with links to Homework Help for Students.

The MII home page is located at

2. Women in Mining Education Foundation

Classifying Minerals Activity which contains student worksheet and instructions for completion, can be found at

3. Mineral Matters from San Diego Natural History Museum

This site offers some practical advice on how to identify minerals, how to turn the pile of rocks and minerals “you” have collected into an organized rock and mineral collection, as well as other practical advice for the those new to mineral and rock collecting.

This site and its activities can be accessed by visiting

4. Minerals Management Service Pacific Region

The Minerals Management Service Pacific Region has a long-standing commitment to work with local educators and students to improve access to scientific information and to increase interest in and an understanding of math and science.

This site can be accessed by visiting,

5. 3D Images of Common Minerals

Indiana University created a fun 3D image gallery. Note: 3D glasses are recommended for viewing.

These images can be viewed at,

6. Specific Gravity Test

An online activity that can be used by students to determine the amount of gold in a nugget that contains other material such as quartz.

This activity and explanation can be viewed at,

7. The Life Cycle of a Mineral Deposit

A Teacher’s Guide for Hands-On Mineral Education Activities. Download this free teacher’s guide and supporting materials at

8. USGS Minerals Information

Find publications of “Minerals Yearbook” 1994-2005 for the state of Nevada. Website also includes links to the Nevada Bureau of Mines & Geology, the Association of American State Geologists, USGS Fact Sheets-Nevada, and USGS Geological Research Activities - Nevada.

9. Webminerals listing of Minerals A-Z

A wealth of information containing details of over 4000 minerals. Each page contains information on the mineral’s chemical formula, composition, crystallography, locality, name origin, physical properties, and includes images.

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Support Pages

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Benchmark Related Vocabulary