J.T. Reddick Elementaryreddick.tiftschools.com/ourpages/auto/2014/7/13/54187673... · Web view2014/07/13  · Igneous rock formed when magma slowly cools beneath the Earth’s surface

Book 2: Minerals and Rocks

Chapter 1: Properties of Minerals

Vocabulary Building

Mineral

Elements

Streak

Luster

Hardness

Mohs scale of hardness

Cleavage

Fracture

Fluorescence

Reactivity

Magnetism

Jack was an avid rock collector. Jack’s family has taken a summer vacation in the Bahamas. While walking on the beach, Jack spotted a few rocks. He picked up three rocks. One has a grainy feel to it, a second had large dark crystals, and a third had a wavy dark band running through it. Jack put the rocks into his pocket, to examine later.

“Dad, I found these interesting rocks while we were on the beach this morning,” said Jack. “Let’s have a look,” replied his dad. Jack showed his dad the rocks. “Well, Jack, you have three different types of rocks here,” dad explained. “These rocks have properties that make them unique. Do you know what make makes up rocks?” asked dad.

“No, dad, what are rocks made of?” Jack asked. “Rocks are made up of different types of minerals. Minerals have properties that make them different from rocks. Jack wanted to find out more about minerals and their properties. Jack went to his room to get his tablet. He began to Google minerals.

. Jack discovered that a mineral is a naturally occurring substance, that is, it is not manmade. A mineral is inorganic, that means that it is not from substances that were once

part of a living thing. A mineral is always a solid. It is not a liquid or a gas. A mineral will have a crystal structure, that is, it will line up in a repeated pattern. A mineral has a definite chemical composition. It will always contain certain elements in definite proportions. These five properties of a mineral is the mineral’s definition. “How can I remember the definition for a mineral?” Jack asked himself. Back in third grade Jack remembered how his teacher taught hi, to visualize pictures and make associations that could help him with word definitions and meaning. Jack thought it would be neat to use an acronym to help him with this. “I got it! I will use the acronym, N C I S ‘D,” exclaimed Jack excitedly.

As Jack researched further, he discovered that there were certain physical properties that geologists use to identify individual minerals. These physical properties are actual tests that can be performed on each mineral for its identification. There are about 4,000 known minerals. Many look very similar, which makes it difficult to tell them apart! There are seven physical properties and four special properties that we will be focus on in this chapter.

Jack went to his father’s study and took down one of his boxes of minerals. Looking at the minerals, Jack looked at the minerals and noticed that a few had similar colors, some were shiny, and the others looked dull and glassy. “How can you tell one mineral from the next?” Jack said to himself. Jack resumed his research. The first physical property test is color. Color is the least reliable and provides the least information about the identity of a mineral. Most mineral have the same color, therefore color will provide the least information and is the least reliable. Streak is the color minerals powder when rubbed against a piece of unglazed porcelain tile. The steak may be the same color of the mineral, a different color, white, or clear /colorless.

Luster describes how light is reflected from a mineral’s surface.

Minerals Density is described as mass per unit volume. The more mass a mineral has, the greater its density. No matter what the size of the mineral is, big or tiny, the density will always be the same.

Hardness is one of the best methods to test for the identity of a mineral is to test for its hardness. The Mohs Scale of Hardness is a scale used to measure the hardness of a mineral. It ranks minerals from 1 to 10 or from softest to hardest. Talc is softest at 1, apatite has a hardness of 5, and diamond is hardest at 10. The hardness is determined by a scratch test using your finger nail, a copper coin, knife, glass, or steal file.

Crystal structure is the repeated pattern or growth of the mineral’s atoms. The crystal structure is based on the number and angle of the crystal faces. The crystal structure maybe described as cubic, hexagonal, tetragonal, orthorhombic, monoclinic, or triclinic.

A mineral has cleavage if it breaks apart evenly and smoothly along a flat surface. A mineral has fracture if it breaks apart unevenly or irregularly, so that it has jagged or pointed edges.

Muscovite

CLEAVAGE

Cleavage in one direction.

Calcite

CLEAVAGE

Cleavage in three

directions not at right

angles (120o and

60o). Rhombohed

ral cleavage.

Quartz

FRACTURE

Mineral does not exhibit

cleavage; it breaks

or fractures

in an irregular manner.

Jack decided to sort his samples according to fracture and cleavage. He realized that some of his samples didn’t fit into any of these categories, and some fit into more than one category. Jack realized that some of his samples had special properties. Some minerals had the special property of fluorescence, the mineral gloves under ultraviolet light. A mineral has optical properties if it has the ability to bend light to produce a double image. A mineral has reactivity if it will frizzle when place in vinegar or a weak acid. A mineral will have magnetism if it attracts paper clips, iron staples, or iron filing. This mineral may contain iron.

Fluorescence

Optical properties

Reactivity

Magnetism

Jack summarizes his findings. The definition of a mineral is the characteristic of a mineral. A mineral is naturally occurring, inorganic, solid with a chemical structure and a definite chemical composition, or N C I S’ D. The physical properties are tests that maybe performed on a mineral to identify a mineral. These physical properties are color, streak, luster, hardness, cleavage, fracture, density, crystal structure. Special properties include fluorescence, optical properties, reactivity, and magnetism.

Discussion questions:

1. Write your own definition of a mineral. Write your own acronym for the definition or characteristic of a mineral.

2. What does it mean to say a mineral is “inorganic” or “naturally occurring”?

3. Name the seven physical properties that can be used to identify a mineral. Name the four special properties that a mineral can have.

4. What is the difference between cleavage and fracture?

Extension: (Analysis/application)

1. Amber is a precious material used to make jewelry. It forms when the resin of pine trees hardens into stone. Is Amber a mineral? Explain your reasoning.

Book 2: Minerals and Rocks

Chapter 2: Classifying Rocks

Vocabulary Building

Mineral composition How many and how much of a mineral or minerals that a rock contains.

Texture The look and feel of a rock.

Rock forming minerals 10-15 different minerals that compose about 90% of all the rocks in Earth's crust.

Coarse grained Slowly cooling magma that makes an igneous rock with large crystals.

Fine grained Texture of an extrusive igneous rock as it cools quickly on the surface of the Earth.

Igneous A type of rock that forms from the cooling of molten rock at or below the surface.

Sedimentary A type of rock that forms when particles from other rocks or the remains of plants and animals are pressed and cemented together.

Metamorphic A type of rock that forms from an existing rock that is changed by heat, pressure, or chemical reactions.

Lithification The process that converts sediments into solid rock by compaction or cementation.

Jack focused his attention to the three rocks that he had collected on the beach. He pulled them from his sample kit located on the shelf in his bedroom. One of the rocks had large dark crystals, a second rock had a grainy feel to it, and a third had a wavy dark band running through it. Jack wanted to find out more about how these rocks were classified. Jack went to find his dad. “Dad, how do geologists identify different types of rocks?” asked Jack. “Rocks are identified by their mineral composition, color, and texture. Since rocks are made up of a mixture of minerals and other substances, these minerals are known as rock forming minerals. There are about twenty minerals that are rock forming minerals. Once we know the mineral composition of the rock, we’ll be able to identify the rock,” answered dad. “How does color help in a rock’s identification?” asked Jack. Jack went to his tablet to research more.

Color provides information to the mineral’s composition. A rock that is light in color will have high silica content. For example, granite is light in color with high silica content. Rocks that are dark in color, like basalt, are low in silica. In addition to color, geologists look at the grains or particles of minerals that make up the rock. Grains will describe a rock’s texture. The rock’s texture is the look and feel of the rock’s surface.

In describing a rock’s texture, geologists examine the grain size, grain shape, and grain pattern. When looking at grain size, geologists look to see if the grains are large and easy to see. If the grains are large and easy to see, then these types of rocks are called coarse-grained. If the grains are small and difficult to see, the rocks are called fine-grained. Some rocks have grains that are not visible even under a microscope. This type of rock is called no visible grain. Grain shape may include shapes of the mineral crystals or rock fragments. These fragments maybe smooth, rounded, or jagged. Grains in a rock often form a pattern. The pattern may be flat layers, swirling, or the grains may be randomly scattered in the rock.

Courses grain

Gabbro

Fine Grain

Basalt Scoria

No visible grain

Obsidian

Jack needed to find out how rocks are classified. He read that the classification is based on the origin of the rock or where the rock was formed. Jack went in search of his dad. “Dad,

can you tell me how rocks are classified?” enquired Jack. “Rocks are classified into three major categories. The classification is based on the origin of the rock itself,” continued dad. “These classifications are igneous, sedimentary, and metamorphic rocks,” explained dad. Jack went to his tablet to find out as much as he could about each classification of rock.

Jack read that igneous rocks are rocks that are formed from the cooling of lava or magma. Sedimentary rocks are formed when particles of other rocks or the remains of plant and/or animals are pressed and cemented together by lithification. These rocks are formed in layers that are buried below the water surface. Metamorphic rocks are formed from any of the three types of rocks that are changed by heat, pressure, or a chemical change in the crystal or grain arrangement. Metamorphic rocks are formed deep underground.

Jack summarized his findings. Rocks are classified according to its mineral composition, color, and texture. Texture is the look and feel of the rock. Texture is described by the grain size, grain shape, and grain pattern. Grain is the particles of minerals that make up the rock. Geologists place rocks into three categories according to their origin. Igneous rocks form the cooling of lava or magma. Sedimentary rocks are formed by compaction and cementation of other rock fragments underwater. Sedimentary rocks are formed in layers. Metamorphic rocks are formed from heat, pressure, and chemical changes deep underground.

Discussion questions:

1. Write about the three characteristics that geologists use to identify rocks.

2. Explain what text is and what factors geologists look at when describing the texture of rocks.

3. Name the three types of rocks. Compare and contrast each type.

4. Research Conglomerate and Breccia, using Google. In your own words, compare the grain size, grain shape, and grain pattern in each of these two types of rocks. Draw an illustration of each.

Extension: (Analysis/application)

1. Gneiss is a group is a kind of rock that forms when heat and pressure inside Earth change granite. To what group of classification of rocks does gneiss belong? Provide evidence to support your answer.

Book 2: Minerals and Rocks

Chapter 3: Igneous Rocks

Vocabulary Building

Extrusive Igneous rock that forms from lava on Earth's surface.

Basalt A dark, dense, igneous rock with a fine texture, found in oceanic crust.

Intrusive A type of igneous rock that generally contains large crystals and forms when magma cools slowly beneath Earth's surface.

Granite A usually light-colored igneous rock that is found in continental crust.

Texture The look and feel of a rock.

Grain size The size of the particles of minerals or other rocks that give a rock its texture.

Grain shape The shape of the particles of minerals or other rocks that give a rock its texture.

Coarse grain Slowly cooling magma that makes an igneous rock with large crystals.

Fine grain Extrusive igneous rock cools rapidly on the earth's surface, these rocks have small crystals called fine grained. an example is basalt.

No visible grain No grains, or grains too small to see even with a microscope. Rock is smooth and shiny.

“What do I already know about igneous rocks,” Jack thought to himself. “I know that igneous rocks are formed from magma or lava. “Well, exactly how do geologists classify different types of igneous rocks?” Jack wondered. Jack went in search of his tablet to Google the information.

According to his research, igneous rocks are classified according to its place of origin, texture, and mineral content. Origin means where the rock is formed. If the rock is formed when lava from a volcano reaches the surface of Earth, the rock is classified as extrusive rock. (“ex” means outside of). Basalt is the most common type of

extrusive igneous rock that covers the Earth’s ocean floors. Igneous rock formed when magma slowly cools beneath the Earth’s surface is called intrusive rock. The most common type of intrusive igneous rock is granite. Granite forms the core of the mountain ranges.

Jack continued his research about texture. Texture is the look and feel of a rock. Texture depends on the size and shape of the grains of the minerals that make up the rocks. Intrusive and extrusive rocks have different textures. Intrusive rocks have large crystal and the crystal can be easily seen. They are described as course grained. Extrusive rocks are fine grained or no visible grain, because the lava cooled so rapidly that the crystal has little or no time to grow. So in some extrusive rocks the crystals are extremely tiny, or have a glassy texture. Jack wanted to find examples of course grained, fine grained, and no visible grain rock.

Rhyolite

Obsidian

Pegmatite

Porphyry

Jack recalls that most minerals contain silica. Silica is a material made from oxygen and silicon dioxide. Silica is a light colored material. If a rock has high silica content, the rock will be light in color. If the rock has low silica content, the rock will be dark in color. A rock’s mineral composition will determine its color.

Granite

“What are some of the uses of igneous rocks?” Jack wondered. He remembered his mom looking through catalogs and rock samples in search of countertops. “What makes igneous rocks useful?” continued Jack. Jack went in search of his dad. “Well Jack, igneous rocks are hard, dense, and durable. These properties make igneous rocks excellent building materials. Igneous rocks are used to make cobble stones, curbstones, kitchen countertops, and floors. Pumice is used as an abrasive to polish surfaces.

Jack summarizes his findings. Igneous rock can be classified according to their place of origin. If the lava cools rapidly on the surface of Earth, the rock is called an extrusive igneous. The lava cooled so rapidly on reaching the surface, the crystals didn’t have time to grow. If the cooling was instantaneous, the rocky will have a glassy texture. Extrusive igneous rocks are described as fine grained or no visible grain. If the magma inside the volcano cooled slowly, the mineral crystal will have lots of time to grow. These rocks are called intrusive igneous rocks. They are described as course grained, because the crystals are large and easy to see.

Discussion questions

1. How are igneous rocks classified?

2. Differentiate between intrusive and extrusive igneous rocks.

3. What characteristics make igneous rocks useful as building material? Give examples of the uses of igneous rocks.

Resource

Geology.com

Book 2: Minerals and Rocks

Chapter 4: Sedimentary Rocks

Vocabulary Building

Sediments Loose materials such as rock fragments, mineral grains, and bits of shell that have been moved by wind, water, ice, or gravity.

Sedimentary rocks A type of rock that forms when particles from other rocks or the remains of plants and animals are pressed and cemented together.

Weathering Chemical or physical process that breaks down rocks into smaller pieces.

Erosion Process by which weathered rock and soil are moved from one place to another.

Deposition Process in which sediment is laid down in new locations

Compaction The processes by which sediments are pressed together under their own weight.

Cementation Cementation is the process in which dissolved minerals crystallize and glue particles of sediment together.

Clastic rocks Sedimentary rock that forms when fragments of preexisting rocks are compacted or cemented together.

Organic rocks Sedimentary rock that forms from the remains of plants or animals.

Chemical rocks Sedimentary rock that forms when minerals precipitate from a solution or settle from a suspension.

Jack strolled along the bank of the stream. He was fascinated by the shiny glistening of the sand. There were tiny sand grains, mud, and pebbles scattered on the bank of the stream. Jack remembered his dad explaining that sediments were small, solid pieces of rock mixed in with pieces of living organisms. Jack thought about how much sediments sound like sedimentary rocks. “How are sediments and sedimentary rocks connected?” Jack wondered. After his stroll along the steam, Jack decided to research sedimentary rocks. Jack reached or his tablet, and began to Google sedimentary rocks. Jack read that sedimentary rocks are formed tough a process called lithification. Lithification is a series of processes including weathering, erosion, deposition, compaction, and cementation. Acronym: WEB2Cs.

Jack decided to investigate further. He began to read more. Weathering is the breaking down of rocks into sediments. Sediments are tiny particles of sand, mud, and pebbles. Erosion is the destructive forces that produce sediments. These forces include heat, cold, water/rain, running water, wind, and ice. These agents can also carry away these sediments to

other locations. Deposition occurs when these sediments are laid down at the bottom of a lake or ocean. Compaction occurs when the sediments are pressed together in layers as they settle to the bottom of a lake /stream, rivers, or ocean. Cementation occurs when these compacted layers are glued together when the crystals of minerals, dissolve in the water, act like a glue.

Sedimentary rocks are classified according to the type of sediments that make up the rock. Jack’s became more interested in finding out the different types of sedimentary rocks. Jack closed his tablet and went to his dad’s library. Jack went to the reference book sections and pulled out a text on sedimentary rocks. Jack skimmed through the table of context, until he came to the heading, Types of Sedimentary rocks. He turned to page 235, and began to read. There are three main types of sedimentary rocks: Clastic sedimentary rocks, organic sedimentary rocks, and chemical sedimentary rocks.

Clastic sedimentary rocks are formed when pieces of rock fragments are cemented together. These particle sizes vary. Common types of sedimentary rocks are shale (made from mud, silt, or clay particles), sandstone (made from sand particles), conglomerate (made from smooth, rounded rock particles), and breccia (made from jagged and sharp pieces of rock particles).

Shale

Sandstone

Conglomerate

Breccia

Organic sedimentary rocks are formed from the remains of plants and animal remains that have been cemented into the rock. “Organic” means once was part of a living thing. Plant and animal remains include shells, bones, teeth, or plant remains. Examples of organic plants are coal and limestone.

Coal

Limestone

Coquina

Chemical rocks are rocks that are formed when the minerals dissolve in water and then crystallize and cement together to form the rock. Chemical rocks can also be formed when water evaporate leaving behind minerals that crystalize and cement to form the rocks. An example of a chemical rock is limestone.

Limestone

Jack realized that sedimentary rocks were not as strong as igneous rocks. He was curious to know the uses of these rocks. Jack skimmed through the table of content, and found the chapter on Uses of Sedimentary Rocks page 368. Jack began to read. Sedimentary rocks are used to make tools like arrowhead made from flint. Sedimentary rocks are used as building material. Sandstone and limestone are easy to cut into slabs and are used to make cement and steel. Jack returned the reference text to the book shelf and returned to his room. Jack lay on his bed to review what he had learned.

Jack summarizes his findings. Sedimentary rocks are classified by the type of sediments that make up the rock. These sediments may include mud particles, sand particles, smooth rock particles, or jagged sharp rock particles. There are three types of sedimentary rocks. Clastic rocks made from sediments, organic rocks made from remains of plants and animal remains, and chemical rocks made when minerals dissolve in water and crystallize to form the rock. Sedimentary rocks are used to make weapons and building material.

Discussion Questions

1. How do geologists classify sedimentary rocks? Name the different types of sediments.

2. Differentiate between clastic, organic, and chemical sedimentary rocks.

3. Place these steps in order during the formation of a sedimentary rock: compaction, erosion, cementation, weathering, and deposition. Write a definition for each step using your own words.

4. What is the difference between conglomerate and breccia? Sketch a diagram of each rock, showing the sediments that make up the rock.

Extension (Synthesis)

1. The particles of sediments that make up shale are not usually well cemented. Do you think shale would be a good choice for building a home, especially in an area with a wet climate? Explain your reasoning.

Resource: Geology.com

Book 2: Minerals and Rocks

Chapter 5: Metamorphic Rocks

Vocabulary Building

Metamorphic rocks Formed from other rocks by the effect of high temperature, high pressure, or chemical conditions different from those of the original formation of the parent rock.

Preexisting Already exists.

Slate The original type of rock before it was changed.

Schist rock A foliated rock that forms when pressure is exerted on the sedimentary rock shale.

Gneiss Are metamorphic. These rocks can be formed from basalt, an igneous rock; shale, a sedimentary rock; or slate, a metamorphic rock. Through tremendous heat and pressure, these rocks were transformed into this new kind of rock.

Parent rock A type of metamorphic rock that usually has ribbon-like layers. Gneiss can often be seen on mountainsides, where rocks formed below the surface have been pushed up by movements in the earth's crust.

After dinner Jack decided to continue his research on metamorphic rocks. “What exactly are metamorphic rocks and how can you classify them? Jack said to himself. Jack went in search of his tablet. “Metamorphic sounds so much like metamorphosis,” whispered Jack in surprise. Jack recalled in second grade that butterflies went under physical changes in the chrysalis to become butterflies. “Maybe metamorphic rock also go through physical changes under the crust to form”, Jack concluded. Jack decided to Google metamorphic rocks.

According to the website, metamorphic rocks can be formed from any preexisting rock, either from an igneous rock, from a sedimentary rock, or from another metamorphic rock. Metamorphic rocks are rocks that form deep under the Earth’s surface. Layers of rocks build up heat from friction, and pressure from the layers of rocks above. As a result of the high heat and pressure, chemical action can also occur. This may cause the mineral grains to change, creating a new type of rock. Geologists classify metamorphic rocks according to the arrangement of the mineral grains that make up the rock.

Jack read further. There are two types of metamorphic rocks: Foliated and non-

Foliated metamorphic rocks. Foliated metamorphic rocks have the mineral grains arranged in parallel layers in the rock. Well known metamorphic rocks include slate (parent shale), schist (parent rock), and gneiss (parent rock granite). These rocks have cleavage. The rock has cleavage if it is able to split apart along these bands.

Slate

from Shale

Schist (has lots of mica minerals)

From shale

Gneiss

from Granite

Marble

from Limestone

Jack was fascinated by the different types of metamorphic rocks. Jack continued is research. In non foliated metamorphic rocks, the mineral grains are arranged randomly in the rock. These rocks do not have cleavage, so they do not split into layers. They fracture in uneven irregular pieces. Examples are quartzite ( parent rock sandstone), and marble ( parent rock limestone). Metamorphic rocks are extremely hard.

“ What are some uses of metamorphic rocks?” Jack asked himeself.

Matamorphic rocks make good building material and sculpture. Jack laid down his tablet to think about all the information he has learned.

Jack summarized his findings. Metamorphic rocks are hard and durable. Metamorphic rocks are formed fromany of the three types of preexisting rocks. Metamorphic roks are formed from heat, pressure, and chemical change in the mineral grains that make up the rock. Metamorphic rocks are classified as foliated or non foliated, depending if the mineral grains are arranged in parallel layers, or arranged randomly in the rock. Metamorphic rocks are formed deep under the Earth’s surface, within the crust.

Discussion Questions

1. In your own words, write a definition for metamorphic rock.

2. How do geologists classify metamorphic rocks? Describe each type, and write an example of each. Sketch a diagram of each.

3. Where and under what conditions do metamorphic rocks form?

Book 2: Minerals and Rocks

Chapter 6: Rock Cycle

Vocabulary Building

Rock Cycle The process by which one rock type changes into another rock type.

Jack enjoys riding his bike with his friends. As they rested along the stream in his back yard, the friends decided to review for their science quiz the following day. One of the vocabulary words for the week was the rock cycle. “What is a cycle,” asked James. “How can we remember the definition of the rock cycle?” chimed in Paul. “Well, think of the wheels on our bikes. The wheel go round and round in a continuous motion,” answered Jack. “The easiest way to remember the rock cycle is to think of it has a series of processes that slowly change one type of rock into another type. Just like the wheel of the bike spin on and one in one continuous motion, the rock cycle is happening all the time and never stops,” jack replied.

After Jack’s friends left, he decided to research more about the rock cycle and how an igneous rock, a sedimentary rock, or a metamorphic rock could change into each of the other three types. Jack reached for his tablet. He Goggled rock cycle.

Jack studied the diagram above. Jack was able to interept each step in the rock cycle diagram. For an igneous rock to form, an existing rock has to melt to form lava or magma. The lava or magma has to be cooled and solidified on the surafce or below the Earth’s surface. For a sedimentary rock to form, there has to be sediments. Sediments are formed by weathering or breaking down of rocks into tiny pieces. These sediemnts are then eroded or carried to new locations by water, wind, ice, or gravity. The sediments are deposited or placed at the bottom of a lake, stream, river, or ocean. As the layers form, enough pressure is built to and press the layers together until they become compacted. The mineral crystals act as a glue, cementing the layers together to make the sedimentary rock. The entire process is called lithification. For metamorphic rocks to form, igneous rock, sedimentary rock, or another metamorphic rockhas to be buried deep underground. The high heat/temperature and pressure cause the mineral grains to change. The change in the mineral grain arrangement will form a new rock called a metamorphic rock.

Jack laid down his tablet, and summarized his findings. An igneous rock is formed when a preexisting rock ( an igneous rock, a sedimentary rock, or a metamorphic rock) melts, cools, and solidifies. A sedimentary rock can be formed from an igneous rock, a sedimentary rock, or a metamorphic rock. The rock will form sediments by weathering. Sediments are then carried to a new location by the process of erosion. The sediments are deposited at the bottom of a lake or an ocean in layers. The pressure of the overlying layers above press or compact the layers together. The mineral crystals in the rock, act like a glue cementing the layers together. A sedimentary rock forms. A metamorphic rock can be formed from an igneous rock, a sedimentary rock, or another metamorphioc rock. The rock has to be buried undergroud, where heat and pressure cause the mineral grains to change.

Discussion Questions

1. In your own words, write a definition for the rock cycle.

2. How can a sedimentary rock change into an igneous rock?

3. How can a metamorphic rock change into another metamorphic rock?

4. How can an igneous rock change into a sedimentary rock?

Extension (Synthesis)

1. Draw the rock cycle showing all the steps in the process.