chapter: rocks and minerals - · pdf filechapter: rocks and minerals ... identify the...

Chapter: Rocks and Minerals

Table of Contents

Section 3: Metamorphic Rocks and

the Rock Cycle

Section 1: Minerals — Earth’s Jewels

Section 2: Igneous and Sedimentary Rocks

Chapter 3: Rocks and Minerals

Table of Contents

Objectives:

What you should be able to do

Section 1: Minerals — Earth’s Jewels 1. Identify the difference between a mineral and a rock

2. Describe the properties that are used to identify minerals

Section 2: Igneous and Sedimentary Rocks 3. Explain how extrusive and intrusive igneous rocks are different

4. Describe how different types of sedimentary rocks form

Section 3: Metamorphic Rocks and the Rock Cycle 5. Describe the conditions needed for metamorphic rocks to form

6. Explain how all rocks are linked by the rock cycle


Table of Contents


Table of Contents

Section 1: Minerals — Earth’s Jewels

1. Identify the difference between a mineral and a rock

2. Describe the properties that are used to identify minerals

Chapter3 : Rocks and Minerals

Table of Contents

Minerals are inorganic, solid materials found in nature. Inorganic= was not alive or living. Material not formed by plants or animals.

Minerals show an orderly arrangement of atoms that looks something like a garden trellis.

What is a mineral?— Minerals Defined

Minerals—Earth’s Jewels

1

The chemical formula (makeup) and arrangement of the

atoms in the crystal identifies each mineral

• Rocks usually are made of two or more minerals.

What is a mineral?— Minerals Defined


1

• Each mineral has unique characteristics you can use to identify it.

• Minerals form in several ways. One way is from melted rock material inside Earth called magma.

• As magma cools, atoms combine in orderly patterns to form minerals.

How do minerals form?


1

• Evaporation can form minerals.

• Just as salt crystals appear when seawater evaporates, other dissolved minerals, such as gypsum, can crystallize.



1

• A process called precipitation can form minerals.

• Water can hold only so much dissolved material.

• Any extra separates and falls out as a solid.



1

• Large mineral grains that fit together like a puzzle seem to show up in rocks formed from slow-cooling magma.

Formation Clues


1

• If you see large, perfectly formed crystals, it means the mineral had plenty of space in which to grow.

Formation Clues


1

• This is a sign they may have formed in open pockets within the rock.

• Each mineral has a set of physical properties that can be used to identify it.

• Most common minerals can be identified with items you have around the house and can carry in your pocket, such as a penny or a steel file.

Properties of Minerals


1

• All minerals have an orderly pattern of atoms.

• The atoms making up the mineral are arranged in a repeating pattern.

Crystals


1

• Solid materials that have such a pattern of atoms are called crystals.

• Minerals that split into pieces with smooth, regular planes that reflect light are said to have cleavage

Cleavage and Fracture


1

• Not all minerals have cleavage. Some break into pieces with jagged or rough edges.

Cleavage and Fracture


1

• Materials that break this way, such as quartz, have what is called fracture (FRAK chur).

• Sometimes a mineral’s color can help you figure out what it is. But color also can fool you.

Color


1

• The common mineral pyrite has a shiny, gold color similar to real gold.

• Because of this, pyrite also is called fool’s gold.

• Scraping a mineral sample across an unglazed, white tile, called a streak plate, produces a streak of color.

Streak and Luster


1

Streak and Luster


1

• The streak is not necessarily the same color as the mineral itself. This streak of powdered mineral is more useful for identification than the mineral’s color.

• Luster describes how light reflects from a mineral’s surface.

Streak and Luster


1

• If it shines like a metal, the mineral has metallic luster.

• Nonmetallic minerals can be described as having pearly, glassy, dull, or earthy luster.

• Friedrich Mohs developed a way to classify minerals by their hardness.

Hardness


1

• The Mohs scale classifies minerals from 1 (softest) to 10 (hardest).

Hardness


1

• You can determine hardness by trying to scratch one mineral with another to see which is harder.

• Specific gravity compares the weight of a mineral with the weight of an equal volume of water.

Specific Gravity


1

• Pyrite—or fool’s gold—is about five times heavier than water. Pure gold is more than 19 times heavier than water.

• Measuring specific gravity is another way you can identify minerals.

• The mineral magnetite will attract a magnet.

Other Properties


1

• The mineral calcite has two unusual properties. It will fizz when it comes into contact with an acid like dilute HCl.

• Also, if you look through a clear calcite crystal, you will see a double image.

• Only a small number of the more than 4,000 minerals make up most rocks.

Common Minerals


1

• Most of the rock-forming minerals

are silicates (contain the elements silicon and oxygen).

Common Minerals


1

• More than half of the minerals in Earth’s crust are types of a silicate mineral called feldspar.

• Other important rock-forming minerals are carbonates.

Common Minerals


1

• The carbonate mineral calcite makes up most of the common rock limestone.

• Gems are minerals that are rare and can be cut and polished, giving them a beautiful appearance.

Gems


1

• To be gem quality, most minerals must be clear with few or no blemishes or cracks.

• A gem also must have a beautiful luster or color.

• gems are rare because they only form under special conditions.

The Making of a Gem


1

• Diamond, for instance, is a form of the element carbon.

• Scientists suggest that diamond forms deep in Earth’s mantle. It takes a certain kind of volcanic eruption to bring a diamond close to Earth’s surface, where miners can find it.

• ore – a type of mineral that contains enough of a useful substance that it can be sold for a profit.

Ores


1

• The iron used to make steel comes from the mineral hematite, lead for batteries is produced from galena, and the magnesium used in vitamins comes from dolomite.

• Ores are removed from the earth by mining.

• After an ore has been mined, it must be processed to extract the desired mineral or element.

Ore Processing


1

• Smelting melts the ore and then separates and removes most of the unwanted materials.

Ore Processing


1

• After this smelting process, it can be refined, which means that it is purified.

Section Check

1 Question 1

List some places you might find minerals

in your home.

Answer

You can find minerals in salt shakers, pencils,

glasses, and ceramic dishes.

Section Check

1 Question 2

Explain the difference between a rock and a gem.

Answer

Gems are rare minerals that can be cut and

polished. They have a beautiful color and lack

cracks or blemishes. Rocks are often cloudy and

when they are cut, they crack.


Table of Contents

Section 2: Igneous and Sedimentary Rocks


Table of Contents

Objectives:


Section 2: Igneous and Sedimentary Rocks 3. Explain how extrusive and intrusive igneous rocks are different

4. Describe how different types of sedimentary rocks form


Table of Contents

Igneous Rock

• Igneous rocks form when melted rock material from inside Earth cools.

• Extrusive igneous rock form when melted rock cools on Earth’s surface.

• Intrusive igneous rock forms when the melted rock cools below Earth’s surface,.

Igneous and Sedimentary Rocks

2

Chemical Composition

• The chemicals in the melted rock material determine the color of the resulting rock.


2

• If it contains a high percentage

of silica and little iron, magnesium, or calcium, the rock generally will be light in color.


• Light-colored igneous rocks are called granitic rocks.


2


• less silica and it contains more iron, magnesium, or calcium, a dark-colored or basaltic rock will result.

• Intrusive igneous rocks often are granitic- light colored

Extrusive igneous rocks often are basaltic- dark colored.


2

Rocks from Melted Rock


2

There are 2 types of rock from melted rock:

1. Extrusive

a. Explosive volcanic eruption

b. Lava flows

2. Intrusive

Rocks from Lava

• Extrusive igneous rocks form when melted rock material cools on Earth’s surface.


2

Rocks from Lava

• When the melt reaches Earth’s surface, it is called lava.


2

Rocks from Lava


2

• Lava cools quickly so large mineral crystals don’t have time to form.

Rocks from Lava

• Extrusive igneous rocks can form in two ways.


2

Rocks from Lava

• In one way, volcanoes erupt and shoot out lava and ash.


2

Rocks from Lava


2

• 2nd way is that large cracks in Earth’s crust, called

fissures can open up and lava oozes out.

Rocks from Lava

• Oozing lava from a fissure or a volcano is called a lava flow.

• The fastest cooling lava forms no grains at all. This is how obsidian, a type of volcanic glass, forms.


2

Rocks from Magma

• Intrusive igneous rocks are produced when magma cools below the surface of Earth.


2

Rocks from Magma • Intrusive igneous

rocks form when a huge glob of magma from inside Earth is forced upward toward the surface but never reaches it.


2

Rocks from Magma

• Intrusive igneous rocks generally have large crystals that are easy to see.

• Some intrusive igneous rocks do not have large crystals that you can see easily.


2

• Others are a mixture of small crystals and larger, visible crystals.

Sedimentary Rocks


2

sandstone

3 basic kinds of sedimentary rock:

1. detrital

2. chemical

3. organic

Sedimentary Rocks • Pieces of broken rock,

shells, mineral grains, and other materials make up what is called sediment.

• Sediment can collect in layers to form rocks. These are called sedimentary rocks.


2

Sedimentary Rocks

• When sediment is carried then dropped, or deposited, by wind, ice, gravity, or water, it collects in layers.

• After sediment is deposited, it begins the long process of becoming rock.


2

• Most sedimentary rocks take thousands to millions of years to form.

Detrital Rocks

• Detrital rocks are made of grains of minerals or other rocks that have been moved and deposited in layers by water, ice, gravity, or wind.

• Other minerals dissolved in water, cement these particles together.


2

Identifying Detrital Rocks


2

sandstone

4 natural ways that sediments are carried:

1. Wind

2. Water

3. Ice

4. Gravity



2

sandstone

4 sizes of pieces that make

detrital sedimentary rock:

1.Smallest – clay size- shale

2. Silt size – rougher- siltstone

3. Sand grain size – sandstone

4. Pebbles - conglomerate



2

sandstone


• The size of the grains is used to identify a detrital sedimentary rock.


2


• The smallest, clay-sized grains feel slippery when wet and make up a rock called shale.


2

• Silt-sized grains make up the rougher-feeling siltstone.


• Sandstone is made of yet larger, sand-sized grains.


2

sandstone

• Pebbles mixed and cemented together with other sediment up rocks called

make

conglomerates

Chemical Rocks

• Chemical sedimentary rock forms when mineral-rich water from geysers, hot springs, or salty lakes evaporates.

• As the water evaporates, layers of the minerals are left behind.


2

• Chemical rocks form from evaporation or other chemical processes.

Organic Rocks

• Chalk and coal are examples of the group of sedimentary rocks called organic rocks.


2

• Living matter

dies, piles up, and then is compressed into rock.

Organic Rocks


2

• If the rock is produced from layers of plants piled on top of one another, it is called coal.

Fossils

• Chalk and other types of fossiliferous limestone are made from the fossils of millions of tiny organisms.

• A fossil is the remains or trace of a once-living plant or animal.


2

Section Check

2 Question 1

What type of rock forms when melted rock

material from inside Earth cools?

A. igneous

B. lava

C. ore

D. sedimentary

Section Check

2 Question 2

What determines the color of igneous rock?

Answer

The chemicals in the melted rock determine the

color of igneous rock.

Section Check

2 Question 3

The photo shows _______ rock.

A. igneous

B. metamorphic

C. sedimentary

D. volcanic


Table of Contents

Section 3: Metamorphic Rocks and the Rock Cycle


Table of Contents

Objectives:


Section 3: Metamorphic Rocks and the Rock Cycle 5. Describe the conditions needed for metamorphic rocks to form

6. Explain how all rocks are linked by the rock cycle


Table of Contents


New Rock from Old Rock

• Many physical changes on and within Earth are at work, constantly changing rocks.

• It can take millions of years for rock to change.

Metamorphic Rocks and the Rock Cycle

3

• Sometimes existing rocks are cooked when magma is forced upward into Earth’s crust, changing their mineral crystals.

• All these events can make new rocks out of old rocks.

Metamorphic Rocks • New rocks that form when existing rocks

are heated or squeezed but are not melted are called metamorphic rocks.


3

Metamorphic Rocks


3

• Granite can change to gneiss.

The sedimentary rocks: sandstone can become quartzite, and

limestone can change to marble.

Types of Changed Rocks

Texture is a physical characteristic helpful for classifying all rocks.


3

Texture differences in metamorphic rocks:

two main groups

1.foliated and

2.nonfoliated.


Foliated rocks:

1. visible layers or

2. elongated grains.


3

• These minerals have been heated and squeezed into parallel layers, or leaves.

• Many foliated rocks have bands of different-colored minerals.


• Nonfoliated rocks do not have distinct layers or bands.


3

• These rocks, such as quartzite, marble, and soapstone, often are more even in color than foliated rocks.

The Rock Cycle • Scientists have created a model called the

rock cycle to describe how different kinds of rock are related to one another and how rocks change from one type to another.


3

Click image to view movie.


Table of Contents


The Journey of a Rock

• A blob of lava that oozes to the surface and cools forms an igneous rock.


3

• Wind, rain, and ice wear away at the rock, breaking off small pieces. These pieces are called sediment.

The Journey of a Rock

• Mineral-rich water seeps through the sediment and glues, or cements, it together. It becomes a sedimentary rock.


3

• Pressure and heat inside Earth can change it into a metamorphic rock.

• Metamorphic rock deep inside Earth can melt and begin the cycle again.

chapter: rocks and minerals - · pdf filechapter: rocks and minerals ... identify the...

Documents