objectives define a mineral. what is a mineral? describe how minerals form. identify the most common...

Objectives• Define a mineral.

What is a mineral?

• Describe how minerals form.

• Identify the most common elements in Earth’s crust.

– mineral

– crystal

– magma

– silicate

Vocabulary

• Minerals play important roles in forming rocks and in shaping Earth’s surface, and a select few have played a role in shaping civilization.

What is a mineral?• Earth’s crust is composed of about 3000

minerals.

What is a mineral?

Mineral Characteristics

A mineral is a naturally occurring, inorganic solid with a specific chemical composition and a definite crystalline structure.

What is a mineral?

Naturally Occurring and Inorganic

– That minerals are naturally occurring means that they are formed by natural processes.

– All minerals are inorganic, meaning that they aren’t alive and never were alive during any part of their existence.


Solids with Specific Compositions

What is a mineral?

– All minerals are solids with definite shapes and volumes.

– Each type of mineral has a chemical composition unique to that mineral.

– Although a few minerals, such as copper, silver, and sulfur, are composed of single elements, the vast majority are made from compounds.

– In some minerals, chemical composition may vary within a well-defined range.


Definite Crystalline Structure

What is a mineral?

– The atoms in minerals are arranged in regular geometric patterns that are repeated again and again.

– A crystal is a solid in which the atoms are arranged in repeating patterns.


Definite Crystalline Structure

What is a mineral?

– At times and fairly rare, a mineral will form in an open space and grow into one large crystal, possibly taking the shape of one of the six major crystal systems.

Cubic

Tetragonal

Hexagonal

Orthorhombic

Monoclinic

Triclinic

Minerals from Magma• Minerals can form from the cooling of magma.

What is a mineral?

Magma is molten material found beneath Earth’s surface.

• The type and amount of elements present in the magma help determine which minerals will form as it cools.

• Small crystals form from rapidly cooling magma and large crystals form from slowly cooling magma.

Minerals from Solution• A given volume of water in a solution can

dissolve only so much of a solid before the water becomes saturated.

What is a mineral?

– If a solution becomes supersaturated, or overfilled, with another substance, mineral crystals may begin to precipitate, or drop out of solution.

– When liquid evaporates from a supersaturated solution, the elements remain behind and may begin to arrange into crystals.

Mineral Groups• About 30 minerals are common in Earth’s crust.

What is a mineral?

• The most common minerals are often referred to as rock-forming minerals because they make up most of the rocks found in Earth’s crust.

• The vast majority of minerals are made up of the eight most common elements.

Mineral Groups

What is a mineral?

Mineral Groups

Silicates

What is a mineral?

– Silicates are minerals that contain silicon and oxygen, and usually one or more other elements.

– Silicates make up approximately 96 percent of the minerals found in Earth’s crust.

– The most common minerals, feldspar and quartz, are silicates.

Mineral Groups

Silicates

What is a mineral?

– One silicon atom attaches to four oxygen atoms to form a silica tetrahedron, a three-dimensional shape structured like a pyramid.

– The basic silica tetrahedron has the ability to share oxygen atoms with other tetrahedron molecules.

– This allows the molecules to combine chemically and structurally in a vast number of ways.

Mineral Groups

Silicates

What is a mineral?

– Some possible arrangements formed by silica tetrahedrons include single chains, double chains, and sheets.

Mineral Groups

Silicates

What is a mineral?

Mineral Groups

Carbonates

What is a mineral?

– Carbonates are minerals composed of one or more metallic elements with the carbonate compound CO3.

– Carbonates are the primary minerals found in rocks such as limestone, coquina, and marble.

Mineral Groups

Oxides

What is a mineral?

– Oxides are compounds of oxygen and a metal.

– Hematite (Fe2O3) and magnetite (Fe3O4) are common iron oxides and good sources of iron.

Mineral Groups

Oxides

What is a mineral?

– Other major mineral groups are sulfides, sulfates, halides, and native elements.

• Sulfides such as pyrite (FeS2) are compounds of sulfur and one or more elements.

• Sulfates such as anhydrite (CaSO4) are composed of elements with the sulfate compound SO4.

• Halides such as halite (NaCl) are made up of chloride or fluoride along with calcium, sodium, or potassium.

• A native element such as silver (Ag) or copper (Cu) is made up of one element only.

Mineral Groups

What is a mineral?

Section Assessment

1. Match the following terms with their definitions.

___ mineral

___ crystal

___ magma

___ silicate

What is a mineral?

A. minerals that contain silicon and oxygen, and usually one or more other elements

B. a naturally occurring, inorganic solid with a specific chemical composition and definite crystalline structure

C. a solid in which the atoms are arranged in repeating patterns

D. molten material found beneath Earth’s surface

B

C

D

A

Section Assessment

2. What are the two ways that minerals can form from a supersaturated solution?

What is a mineral?

Mineral crystals can precipitate, or drop out of solution if the solution becomes supersaturated. Minerals can also form when liquid evaporates from a supersaturated solution leaving behind the elements which may begin to arrange into crystals.

_______ There are about 30 common minerals in Earth’s crust.

_______ Slowly cooling magma produces small crystals.

_______ Coal is a mineral.

_______ Silicates are the most common minerals on Earth.

_______ Well-defined crystal shapes are rare.

Section Assessment

3. Identify whether the following statements are true or false.

What is a mineral?

true

false

false

true

true

Objectives• Classify minerals according to their physical and

chemical properties.

• Identify different types of minerals.

• Discuss how minerals are used.

– luster

– streak

– hardness

– cleavage

– fracture

– specific gravity

– ore

– gem

Vocabulary

Identifying Minerals

Mineral Identification• Geologists rely on several relatively simple tests

to identify minerals.


• These tests are based upon a mineral’s physical and chemical properties.

• It is usually best to use a combination of tests rather than just one to identify minerals.

Mineral Identification

Color


– One of the most noticeable characteristics of a mineral is its color.

– Color is sometimes caused by the presence of trace elements or compounds within a mineral.

– In general, color is one of the least reliable clues to a mineral’s identity.


Luster


– Luster is the way that a mineral reflects light from its surface.

– Luster is described as being either metallic or nonmetallic.

– Metallic luster describes shiny surfaces that reflect light like the chrome trim on cars.

– Nonmetallic luster might be described as dull, pearly, waxy, or silky.

– Differences in luster are caused by differences in the chemical compositions of minerals.


Texture


– Texture describes how a mineral feels to the touch.

– The texture of a mineral might be described as smooth, rough, ragged, greasy, soapy, or glassy.


Streak


– Streak is the color of a mineral when it is broken up and powdered.

– Sometimes, a mineral’s streak does not match the mineral’s external color.

– A mineral’s streak rarely changes, even if it is weathered or its external color varies slightly.


Hardness


– Hardness is one of the most useful and reliable tests for identifying minerals.

– Hardness is a measure of how easily a mineral can be scratched.

– German geologist Friedrich Mohs developed a scale in which an unknown mineral’s hardness can be compared to the known hardnesses of ten minerals.

– Any mineral with a greater hardness than another mineral will scratch that softer mineral.


Hardness



Cleavage and Fracture


– Minerals break along planes where atomic bonding is weak.

– Cleavage is the ability of a mineral to split relatively easily and evenly along one or more flat planes.

– To identify a mineral by cleavage, geologists count the number of cleaved planes and study the angle or angles between them.

– Fracture is the ability of minerals to break with arclike, rough, or jagged edges.


Density and Specific Gravity


– Differences in weight are the result of differences in density, which is defined as mass per unit of volume.

– Density is expressed as a ratio of the mass of a substance divided by its volume, or D = M/V.

– Density reflects the atomic weight and structure of a mineral.

– The most common measure of density used by geologists is specific gravity.

– Specific gravity is the ratio of the weight of a substance to the weight of an equal volume of water at 4°C.

Special Properties• Special properties of minerals also can be used

for identification purposes.


– A type of calcite called Iceland spar causes light to be bent in two directions, a process known as double refraction, when it passes through the mineral.

– Calcite (CaCO3) fizzes when it comes into contact with hydrochloric acid (HCl).

– Magnetite, an iron ore, is naturally magnetic.

– The mineral sphalerite produces a distinctive rotten-egg odor when it is rubbed vigorously across a streak plate.

Mineral Uses• Minerals are virtually everywhere.


• They are used to make computers, cars, televisions, desks, roads, buildings, jewelry, beds, paints, sports equipment, and medicines, just to name a few uses.

Mineral Uses

Ores


– An ore is a mineral that contains a useful substance that can be mined at a profit.

– Examples of ores include Hematite, which contains the element iron and bauxite, which contains the element aluminum.

Mineral Uses

Mines


– Ores are removed by underground mining or from large, open-pit mines.

– When a mine is excavated, unwanted rock and dirt, known as waste material, are dug up along with ore.

– If the cost of separating the waste material becomes higher than the value of the ore itself, then the mineral will no longer be classified as an ore because it would no longer be economical to mine it.

– The classification of a mineral as an ore may also change if the supply of or demand for that mineral changes.

Gems

Gems are valuable minerals that are prized for their rarity and beauty.


• Gems such as rubies, emeralds, and diamonds are cut, polished, and used for jewelry.

• In some cases, the presence of trace elements can make one variety of a mineral more colorful and thus more prized than other varieties of the same mineral.

Section Assessment

1. Match the following terms with their definitions.

___ streak

___ hardness

___ cleavage

___ fracture


A. the ability to break with arc-like, rough, or jagged edges

B. the ability to split relatively easily along one or more flat planes

C. the color of a mineral when it is broken up and powdered

D. a measure of how easily a mineral can be scratched

C

D

B

A

Section Assessment

2. How would an oversupply of ore possibly change the mineral’s classification as an ore?


If an ore is over supplied, it could drive down prices for the ore. This may create a situation in which it would no longer be economical to mine material, thus the material would no longer be classified as an ore.

Section Assessment

3. What is specific gravity?


Specific gravity is the ratio of the weight of a substance to the weight of an equal volume of water at 4ºC. It is a common measure of density used by geologists.

Chapter Resources Menu

Chapter Resources Menu

Study Guide

Section 4.1

Section 4.2

Chapter Assessment

Image Bank

Section 4.1 Main Ideas• A mineral is a naturally occurring, inorganic solid with a

specific chemical composition and a definite crystalline structure. There are at least 3000 known minerals in Earth’s crust.

• A crystal is a solid in which the atoms are arranged in repeating patterns. The six main crystal systems are cubic, tetragonal, hexagonal, orthorhombic, monoclinic, and triclinic.

• Minerals form from magma or from supersaturated solution. Most minerals are formed from the eight most common elements in Earth’s crust.

Section 4.1 Study Guide

Section 4.1 Main Ideas• Oxygen readily combines with other elements to form a

diverse group of minerals, including silicates, carbonates, and oxides. A silica tetrahedron is a three-dimensional shape structured like a pyramid. In a silica tetrahedron one silicon atom attaches to four oxygen atoms.

• Other major mineral groups include sulfides, sulfates, halides, and native elements. Native elements such as silver or copper are made of one element only.


Section 4.2 Main Ideas• Minerals can be identified based on their physical and

chemical properties. The most reliable way to identify a mineral is by using a combination of several tests.

• A mineral’s color is generally the result of trace elements within the mineral. Texture describes how a mineral feels, and luster describes how a mineral reflects light. Cleavage and fracture describe how minerals break.

• A mineral’s streak, hardness, and density are reliable methods of identification. Special properties of minerals such as magnetism also can be used for identification purposes.


Section 4.2 Main Ideas• An ore contains a useful substance that can be mined at a

profit. If the cost of mining the ore becomes higher than the value of the ore, then the mineral is no longer classified as an ore. The classification of a mineral as an ore may also change if the supply of or demand for the mineral changes.

• Gems are valuable minerals that are prized for their rarity and beauty. Trace elements can make one variety of a mineral more valuable than other varieties of the same mineral.


1. What special property can be used to help identify the mineral sphalerite?

a. It fizzles when it comes in contact with HCl.

b. It exhibits double refraction.

c. A rotten-egg odor is produced during a streak test.

d. It is naturally magnetic.

Multiple Choice

Chapter Assessment

Calcite reacts with HCl. Iceland spar and zircon exhibit double refraction when light is passed through them. Magnetite is naturally magnetic.

2. A mineral with a metallic luster could be described as ___.

a. silky c. pearly

b. shiny d. waxy

Silky, pearly, and waxy can all be used to describe nonmetallic luster.

Multiple Choice

Chapter Assessment

Multiple Choice

3. Which ore is a source of iron?

a. bauxite c. zircon

b. rutile d. hematite

Chapter Assessment

Bauxite is an aluminum ore. The ore rutile is a source of titanium. Zircon contains no iron.

Multiple Choice

4. A silica tetrahedron contains ___ oxygen atoms.

a. one c. three

b. two d. four

Chapter Assessment

A silica tetrahedron is made up of one silicon atom bonded to four oxygen atoms.

Multiple Choice

5. Which of the following is an example of native element mineral?

a. halite c. copper

b. pyrite d. anhydrite

Chapter Assessment

A native element mineral is made up of only one element. Halite (NaCl), pyrite (FeS2), and anhydrite (CaSO4) all contain more than one element.

Short Answer

6. Why are crystals that form in well-defined shaped fairly rare?

Chapter Assessment

Most crystals form in restricted space.

Short Answer

7. What are the characteristics of minerals?

Chapter Assessment

To be a mineral, a material must be a naturally occurring, inorganic solid with a specific chemical composition, and a definite crystalline structure.

True or False

8. Identify whether the following statements are true or false.

______ About 90 known elements occur naturally in Earth’s crust.

______ Oxides are compounds of oxygen and another gas.

______ Pyrite has a hexagonal crystal system.

______ Ores must be mined at a profit.

______ Rubies are more valuable than diamonds.

Chapter Assessment

true

false

false

true

true

Image Bank

Chapter 4 Images

Cubic

Tetragonal

Hexagonal

Orthorhombic

Monoclinic

Triclinic

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objectives define a mineral. what is a mineral? describe how minerals form. identify the most common...

Documents

mineral crystals

type of mineral

mineral groups silicates

mineral groups oxides

mineral groups carbonates

major mineral groups

mineral characteristics

magma minerals