unit minerals and rocks

Unit 6

Minerals and Rocks Table of Contents

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Table of Contents

Introduction

Essential Questions

Review

Lesson 6.1: Rock-Forming Minerals 5 Objectives 5 Warm-Up 5 Learn about It 7 Examples 22 Key Points 23 Web Links 23 Check Your Understanding 24 Challenge Yourself 25

Lesson 6.2: Igneous Rocks 26 Objectives 26 Warm-Up 26 Learn about It 27 Examples 34 Key Points 34 Web Links 34 Check Your Understanding 35 Challenge Yourself 36

Lesson 6.3: Sedimentary Rocks 37 Objectives 37 Warm-Up 37 Learn about It 38 Examples 43 Key Points 44

Web Links 44 Check Your Understanding 45 Challenge Yourself 46

Lesson 6.4: Metamorphic Rocks 47 Objectives 47 Warm-Up 47 Learn about It 48 Key Points 53 Web Links 54 Check Your Understanding 55 Challenge Yourself 56

Laboratory Activity 57

Performance Task 58

Self Check 60

Key Words 60

Wrap Up 61

Photo Credits 61

References 63

Copyright © 2018 Quipper Limited2

GRADE 11/12 | EARTH AND LIFE SCIENCE

Unit 6

Minerals and Rocks

What comes to your mind when you hear the word mineral? Is it a commercial advertising a medicine with extra vitamins and minerals? Do you picture miners collecting gold nuggets or a dazzling stripe through a rock surface? Or a multi-faceted attractiveness of a friend’s diamond ring?

Minerals are more than those things. Everyone depends on minerals to accomplish things in their everyday living. For instance, think of your usual morning routine going to school. As you wake up in the morning, you turn off your alarm clock which is made from silica, talc, limestone, mica, and clays. Then you look out of the window, which is manufactured from limestone, dolomite and other minerals, to check if the weather is fine. After getting out of bed, you make your way to the shower in which the knob is made from quartz/silica, feldspar, and kaolin.


Afterwards, you brush your teeth with a toothbrush which is composed of mica, talc, limestone and petroleum products. Then you eat hard boiled egg with high levels of calcium prepared by your mom, you fixed your things and now ready to go to school. Therefore, a day in your life shows how important minerals are. Would your life be different without these things?

Rock, on the other hand, is typically defined by geologists as a combination of naturally occurring substances, mainly minerals. It has long histories, unlike animals and plants. Rocks seem prehistoric and everlasting because within our lifetimes, they are not altered that much. There are three main types of rock based on origin - igneous rocks from magma, sedimentary rocks from sediments and metamorphic rocks from transformed igneous and sedimentary rocks caused by a change in pressure and temperature.

Essential Questions

At the end of this unit, you should be able to answer the following questions.

● What is the importance of minerals in our daily life?● What are the distinct characteristics of each mineral that makes them

different from one another?● What is the difference between the three types of rock?● How each rock type is formed over time?● What are the primary differences between each rock type?

Review

● The outermost and thinnest layer of Earth is the crust.● Directly below the crust is the mantle with a thickness of approximately

2 900 kilometers.● The core is the innermost layer of Earth with a radius of about

3 480 kilometers. The outer core is molten while the inner core is solid.● Magma is a hot fluid beneath or within Earth’s crust.


Lesson 6.1: Rock-Forming Minerals

Objectives In this lesson, you should be able to:

● identify common rock-forming minerals using their physical andchemical properties; and

● identify the minerals important to society.

The relationship between minerals and rocks is like the rocky road ice cream. It is composed of different ingredients: chocolate, marshmallows, peanuts, and almonds. A rock is a combination of unique set of minerals with properties that differentiate them from others. The mineral components varied because of chemical components and structure creating unique physical properties that allows them to be classified. What are these distinct properties that make each mineral unique?

Warm-Up

Mineral Supertrump Card Game The "Mineral Supertrump Card Game" is a modified version of the classic UNO card game. The mineral cards are like the number cards in the typical UNO game while the power cards are like the “supertrump” cards. There are 54 mineral cards and 6 “supertrump” cards.


● Click this link made by the Mineralogical Society of USA to access the whole set of cards. Mineralogical Society of USA. 2016. ‘Mineral Supertrumps - the Game.’ http://www.minsocam.org/msa/Special/mineralsupertrumps_cards.pdf

Material

● Print-out of mineral “supertrumps” cards Procedure:

1. A dealer will give eight cards to each player. 2. The first player will choose a mineral card on hand and put it on a table. The

mineral name and one of the five trump categories (hardness, specific gravity, cleavage, crustal abundance, and economic value) together with its value should be stated. For example, quartz has a specific gravity of 2.65 (or quartz, specific gravity, 2.65).

3. The next player should then place a card with a higher value of the trump category given by the first player. In relation to the previous example, the next player should put down a mineral card with a specific gravity higher than 2.65. The game continues with the next player and so on.

4. The player can pass if ever he has no card with a higher value. He should then pick one card from the table. This certain player will lose a turn.

5. If a player has a supertrump card (The Miner, The Geologist, The Geophysicist, The Petrologist, The Mineralogist, The Gemmologist), they can use it at any of their turns. By using this card, the trump category can be changed based on the instructions on the card. Ex: "The Mineralogist" changes the category to cleavage. This player will then put a mineral card based on the supertrump category given to resume the game.

6. The winner of the game is the first one to lose all their cards. Guide Questions:

1. Based on the activity, enumerate the five trump categories found in each mineral card.

2. Which mineral card is best to use in each trump category? 3. Which mineral card is worst to use in each trump category? 4. Without looking at the cards again, list down 10 minerals that you can

remember.

Copyright © 2018 Quipper Limited

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http://www.minsocam.org/msa/Special/mineralsupertrumps_cards.pdf

http://www.minsocam.org/msa/Special/mineralsupertrumps_cards.pdf

Learn about It

A mineral is a naturally occurring, inorganic, homogeneous solid, with a definite chemical composition, and an ordered crystalline structure. Most minerals have distinctive characteristics. Some minerals, however, are very similar that their physical properties should be examined further to make a correct identification. Physical Properties of Minerals There are several laboratory and field techniques being used to distinguish minerals based on physical properties. Some minerals are too small to be identified by the naked eye that is why there is a need for high-powered instruments such as a petrographic microscope and X-ray diffractometers (XRDs). On the other hand, there are minerals that are large enough to be assessed based on their physical properties. Geologists commonly use physical properties such as color, streak, luster, crystal habit, cleavage, fracture, hardness, and specific gravity to identify minerals. Color Color refers to certain wavelengths of light that are reflected by the material, in this case, a mineral and is perceived by the observer. It is the most noticeable physical property of a mineral and is often the first thing that people consider when looking for minerals as gemstones for jewelry. However, using this as sole basis for mineral identification is not enough because different minerals can have the same color. In addition, color is highly affected by impurities or light diffraction. Mineral colors can be classified into idiochromatic, allochromatic and pseudochromatic. Self-colored minerals are called idiochromatic minerals. Their color is a diagnostic property. This means that the color of a mineral is constant and it depends on the elements that make up their chemical structure. Examples are malachite (always green), rhodochrosite (always red) and sulfur (always yellow).


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Fig. 1. Idiochromatic minerals. From left to right: malachite (green); rhodochrosite (red); and sulfur (yellow)

For allochromatic minerals, color is not a reliable diagnostic property since small impurities may dramatically alter their color. For example, quartz may occur in different varieties. This includes colorless, milky, smoky, citrine, amethyst, and rose as shown below. Allochromatic minerals are often weakly-colored or colorless in their pure state, which allows impurities to pervade them with color. By contrast, idiochromatic minerals are strongly colored which drowns out any impurities in color.

Fig. 2. Varieties of quartz. From top left to bottom left: colorless, milky, smoky,

citrine, amethyst, and rose.


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Lastly, pseudochromatic minerals are false-colored minerals. Their colors are due to light diffraction. In this instance, color may be variable but is an exclusive properties of the mineral.

Fig. 3. Pseudochromatic minerals. From left to right: bornite, labradorite, and opal.

Streak The streak is the color of the powdered form of a mineral. It is observed by rubbing the mineral across a streak plate. As shown below, the color of the mineral is not always the same as the streak color. For mineral identification, this property is more reliable than the color of the mineral since streak is always the same.

Fig. 4. Streak of different minerals. From left to right: sulfur, chalcanthite, azurite, and sphalerite

Luster Luster is the appearance of a mineral’s surface and is dependent on how it reflects light. Common luster types are pearly, silky, dull, resinous, earthy, adamantine, vitreous or glassy, and metallic. Refer to the Fig. 5 and Table 1 for the description of each type.


Fig. 5. Types of luster. From top left to bottom left: talc (pearly); chrysotile (silky);

microcline feldspar (dull); sulfur (resinous); azurite (earthy); diamond (adamantine); dioptase (vitreous); and pyrite (metallic)

Table 1. Types of luster.

Type of Luster Description

pearly Minerals appear the same as a pearl or the abalone shell’s interior.

silky It shows similar properties with silk which has fine parallel threads.

dull A mineral has a plain-looking sheen.

resinous Its characteristics are the same with a resin or chewing gum.

earthy Minerals are opaque and looks like Earth or dirt.

adamantine Minerals are very shiny and brilliant.

vitreous or glassy

Vitreous luster occurs if it has the same sheen as a glass.

metallic A mineral has the same appearance as a polished metal.

Crystal Habit Crystal habit is the characteristic shape in which a mineral grows and is a projection of the mineral’s crystal structure. Some common habits are acicular, blocky, tabular, fibrous, bladed, dendritic, and prismatic as shown below. Refer to Fig. 6 and Table 2 for the description of each type.


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Fig. 6. Different crystal habits. From top left to bottom left: natrolite (acicular);

oligoclase (blocky); barite (tabular); okenite (fibrous); actinolite (bladed); copper (dendritic); and indicolite (prismatic).

Table 2. Types of crystal habit.

Crystal habit Description

acicular Needle-like. Its size is wider than fibrous but thinner than prismatic.

blocky Its shape is rectangular, but the sides are not necessarily flat.

tabular Tablet-like. It has flat squares.

fibrous Furry-like. Its sides are thinner than acicular.

bladed Its shape is like a knife.

dendritic Plant-like.

prismatic Pencil-like. Its sides are thicker than acicular.

Cleavage Cleavage is the tendency of some minerals to break along flat surfaces. These surfaces have the weakest atomic bonding which means that when you use a hammer to break a mineral, it will always break along thispoints. Cleavage surfaces tend to occur repetitively as parallel planes at crystal breaks, which constitute a set,


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or direction of cleavage. The illustration below shows some of the types of cleavage planes.

Fig. 7. Types of cleavage planes .

Fig. 8. Types of cleavage. From top left to bottom left: muscovite (basal); augite (prismatic); hornblende (non-prismatic); halite (cubic); calcite (rhombohedral);

fluorite (octahedral); spharelite (dodecahedral).

Table 3. Types of Cleavage

Type of cleavage Number of cleavage Description

basal one planes on top of the other

prismatic two

cleavage at right angles

non-prismatic cleavage not at right angles


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cubic three

cleavage at right angles

rhombohedral cleavage not at right angles

octahedral four

formed 8 faces

sphalerite formed 12 faces

Fracture Fracture is the pattern in which the mineral breaks aside from its planes of cleavage. This happens when the atomic bonds are of equal strength. Unlike cleavage, fracture does not break along planes; it just breaks unevenly. Various types of fractures exist in nature such as conchoidal, jagged, uneven and splintery.

Fig. 9. Types of fracture. From left to right: obsidian (conchoidal);

copper (jagged); and kyanite (splintery).

Table 4. Types of fracture.

Types of fracture Description

conchoidal Fracture looks like a semi-circular shell.

jagged Fracture appears as jagged points. It has sharp and rough surface.

splintery Splintery-fibrous-like fracture

uneven Rough and irregular fracture. Common in most minerals.


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Hardness Hardness is the resistance of the minerals to scratching. It is measured by scratching the mineral with another object of known hardness. For more accurate measurement, Mohs scale of hardness is used which is composed of ten minerals, numbered from 1 to 10 (1 as the softest and 10 as the hardest). The Mohs scale is a relative scale, not qualitative, which means that gypsum (H=2) is not twice as hard as talc (H=1), only that gypsum is harder than talc.

Fig. 10. Mohs scale of hardness.

The Mohs scale of hardness was named after its proponent, Friedrich Mohs. Mohs was born on January 29, 1773, in Gernrode, Germany. His early studies largely focused on Physics, Chemistry, and Mathematics but later on, he took advanced studies in the mining academy. His interest in mineralogy was inspired by one of his professors named Dr. Werner. In 1801, he became a curator of a private mineral collection owned by a banker named J.F. van der Null. He was required to arrange the minerals into categories, so he started studying the different physical


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properties of these minerals. He discovered the varying hardness of the minerals and later on designed a systematic classification of this property using a scratch test.

Specific Gravity Specific gravity is the ratio of a minerals’ weight to the weight of an equal volume of water. Therefore, a specific gravity of 4 means that a certain substance is four times heavier than water. The size of the mineral is independent of its specific gravity. This means that a larger sample can still yield a smaller specific gravity. The table below shows some of the specific gravity of common minerals. Notice that diamond, the hardest mineral, has a low specific gravity.

Table 5. Specific gravity of some minerals.

Mineral Specific Gravity

talc 2.8

diamond 3.5-3.53

copper 8.95

silver 10-11

mercury 13.6

gold 15-19

Chemical Properties of Minerals All minerals can be represented by a chemical formula, which presents the proportions of atoms that constitute them. For example, the mineral quartz has a chemical formula SiO2. Its crystal structure is a continuous framework of silicon-oxygen tetrahedra.


The chemical properties of minerals depend on their chemical formula and crystal structure. Solubility and melting point are chemical properties commonly used to describe a mineral. Solubility Solubility refers the ability of a substance to dissolve in a solvent at a specified temperature. For example, biotite, a mineral commonly found in igneous rocks, is soluble in both acid and base solutions. The dissolution releases the loosely-bound potassium ions in the mineral. Melting Point

The melting point refers to the temperature at which solid turns into liquid. Minerals composed of atoms that are tightly bonded within the crystal structure have high melting points. For example, quartz melts above 1670°C. Mineral Groups Determined by Chemical Composition Thousands of minerals have been identified and in order to study them closely, geologists group them based on their chemical composition. Table 6 shows the nine broad mineral groups and their description.

Table 6. Nine groups of minerals.

Chemical structure

Description Example Minerals

elements Most of the minerals here are composed of only one element. Having knowledge about elements enables scientists to identify bonding possibilities and compounds that can be created.

copper, gold, silver, sulfur


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sulfides Minerals under these group are composed of a metal joined by a sulfur. Metallic luster is the characteristic that distinguish them.

cinnabar (HgS), pyrite

(FeS2)

halides These are nonmetal groups which consists of chlorine, fluorine, bromine, and iodine as their main chemical constituent.

fluorite (CaF2), halite (NaCl),

diabolite

oxides and hydroxides

These are mineral groups composed of one or more metals joined with oxygen, water, or hydroxyl (OH)

cuprite (Cu2O), hematite (Fe2O3)

nitrates, carbonates,

borates

It is formed when a metal is combined with carbon, nitrogen and boron.

malachite, nitratine,

borax

sulfates One or more metal is combined with a sulfate compound (SO4)

anhydrite (CaSO4)

chromates, molybdate, tungstates

chromate, molybdate, or tungstate substituted the place of the sulfate group. These minerals are usually brightly colored, brittle and dense.

wulfenite (PbMoO4), scheelite (CaWO4)

phosphates, arsenates, vanadates

One or metal is chemically combined with the Phosphates, arsenates, vanadates group.

apatite, lazulite,

vanadinite

silicates This is the largest mineral group. Minerals under this group have different amounts of silicon and oxygen

dioptase, labradorite

Analysis of the Composition and Crystal Structure of Minerals In the laboratory, the composition and crystal structure of minerals can be analyzed through chemical and instrumental analysis. Chemical composition is investigated using wet chemical analysis and several spectroscopic techniques. Wet Chemical Analysis The wet chemical analysis involves dissolving a mineral in an acid and analyzing the solution. An acid used is usually hydrochloric acid (5-10%). If a bubble is evident


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after putting drops of the acid, it indicates that carbonate minerals such as calcite and dolomite is present. The table below shows the reaction of common carbonate minerals to acids.

Table 7. Reaction of some carbonate minerals to acids.

Mineral Chemical composition Reaction to cold

acid Reaction to warm acid

aragonite CaCO3 strong strong

azurite Cu3(CO3)2(OH)2 yes strong

calcite CaCO3 strong strong

dolomite CaMg(CO3)2 weak yes

Spectroscopic Techniques Spectroscopic techniques involve quantitative analysis of mineral components depending on the light absorbance of the compounds. These test the sample’s interactions with electromagnetic radiation to determine its structural and chemical properties. The types of spectroscopic techniques are listed below.

1. Atomic absorption spectroscopy (AAS) uses a controlled flame to separate the components of a sample and monochromator linked to a detector to search for wavelengths of light that are absorbed by the sample. This technique identify the concentration of mineral in a sample.

2. Inductively coupled plasma (ICP) spectroscopy uses argon gas to move the sample vapor into a chamber under high vacuum where both the sample and the gas are heated for the elements to give off a characteristic wavelength of light. This technique is able to trace and identify almost all the minerals present in the sample.

3. X-ray fluorescence (XRF) spectroscopy uses high voltage electrons toward a metal target to produce a specific wavelength X-ray beam that hits the


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sample. Comparing the sample intensities to that of the standard can be used to calculate the concentration of elements present in the mineral. This technique will give an analyst a real-time rock analysis. This is more convenient and efficient than the older technique which takes weeks before analysis is presented.

4. X-ray diffraction spectroscopy (XRD) is a technique that only applies to pure amorphous or crystalline substances and is used to study the structure of the crystals. This process is done by firing an X-ray beam at a finely-ground sample at different angles. Then reflected or diffracted rays can be used to compute for the dimensions of the unit cell. This technique is used to obtain information from unknown crystalline substances particularly most minerals.

Common Rock-Forming Minerals The common rock-forming minerals are quartz, feldspar, mica, pyroxene, amphibole, and olivine. All of the following silicate minerals, except for quartz, are mineral groups.

Quartz Quartz has a chemical composition of SiO2. It is a glass-like hard substance with white streaks. It has Mohs hardness of 7 which makes the quartz grains resist scratching of nail or a pocket knife. Pure quartz is also known as “rock crystal” that is colorless and transparent. Trace amounts of impurities cause colored varieties of quartz. Quartz can occur as amethyst (purple-violet), citrine (yellow), smoky or cairngorm (brown), morion (black), rose (pink), sapphire quartz (blue), and milky (semi-translucent white). The grains of quartz, in general, are irregular in shape and exhibits conchoidal fracture.

Feldspar Feldspar has a chemical composition of XAlSi3O8, where X is potassium (K), calcium (Ca), or sodium (Na). It is quite hard with a Mohs hardness of 6. It is a light-colored mineral, usually white, but can also exist in lighter shades of red or green. It has a glassy luster. In rocks, feldspar forms rectangular crystals that break along flat faces.


1. Plagioclase feldspar (NaAlSi3O8 or CaAl2Si2O8) is the most common mineral in igneous rocks. Most plagioclase appears frosty white to dark gray. Using a hand lens, one can often see the stair-step like cleavage and possible striations or parallel grooves.

Fig. 12. Plagioclase

2. Potassium feldspar (KAlSi3O8) commonly occurs as slightly pinkish grains. Unlike plagioclase, it does not contain striations on its cleavage faces. It also has two cleavage planes both at 90°.

Fig. 13. Potassium Feldspar

Mica Mica is any group of hydrous potassium aluminum silicate minerals. Mica is soft, with hardness ranging from 2 to 2.5. It is easily identified by its perfect cleavage, reducing it to thin smooth flakes. Its luster is responsible for the flashes of light in rocks such as granite and slate.

1. Muscovite mica [KAl3AlSi3O10)(OH)2]

occurs as a white, shiny and silvery mineral. It has a pearly to vitreous luster, white streak and often sheds into tiny flakes when scratched.

2. Biotite mica [K2(Mg,Fe)3AlSi3O10(OH,O,F)2] is black, dark green, or dark brown,

shiny, and often occurs in small-hexagonal crystals. It has a vitreous luster, flaky habit and white to gray streak. Biotite sheets are elastic when bent.


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Pyroxene Pyroxene minerals have a general composition of XY(Al,Si)2O6 where X is calcium (Ca) or magnesium (Mg) and Y is either magnesium (Mg), iron (Fe), or aluminum (Al). It occurs as short, stubby and black to dark-green crystals (although other colors may occur). It has a glassy luster with streaks of white, light green, or light brown. It has good cleavage in two directions (both at almost 90°) and cleavage surfaces are often hard to see in a regular rock sample. Augite is the most common mineral of this group.

Fig. 15. Pyroxene

Amphibole Amphibole has a general formula of W0-1X2Y5Z8O22(OH)2 and has a dark color with a Mohs hardness ranging from 5 to 6. It is opaque and has a glassy luster. It occurs as long and slender crystals. It has good cleavage in two directions (approximately 60°and 120°) and therefore has a stair-step appearance under a hand lens. Hornblende is the most common amphibole.

Fig. 16. Amphibole

Olivine Olivine is a silicate mineral with a general chemical composition of (Mg,Fe)2SiO4, but calcium, manganese, and nickel can be substituted for magnesium and iron. It occurs as small, light green, glassy crystals. It is commonly used in the gemstone industry as peridot. It is a glassy looking and transparent substance that is almost as hard as quartz. Its sugary or sacharroidal texture and olive-green color make it distinctive from other rock-forming minerals. Fig. 17. Olivine


Examples

The table below shows more examples of common minerals and their color, streak, and luster.

Table 8. Physical properties of some common minerals.

Mineral Color Streak color Luster

gold yellow golden yellow metallic

corundum blue (sapphire), red (ruby)

white vitreous to adamantine

graphite dark gray to black dark gray to black dull metallic

fluorite colorless, purple, green, white,

yellow, pink, red, blue, black

white vitreous

galena lead-gray lead-gray metallic


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Key Points

● A mineral is a naturally occurring, inorganic, solid material that has a fixed structure and a definite chemical composition.

● The physical properties of minerals are color, streak, luster, crystal habit, cleavage, fracture, hardness, and specific gravity. These properties are used for mineral identification.

● Solubility and melting point are chemical properties commonly used to describe a mineral.

● The most common rock-forming minerals are quartz, feldspar, mica, pyroxene, amphibole, and olivine.

Web Links

For further information, you may check the links below.

● Click this link to play a game. The goal is to escape from thecastle. Use your knowledge of the Mohs scale to identify whichones will be the easiest to drill throughCool Science Lab. n.d. ‘Mohs’ Drill.’http://coolsciencelab.com/mohs_drill.htm

● Practice your knowledge of the properties of minerals by clicking link.Wiley n.d.. ‘Virtual Rock Lab Interactivity.’https://www.wiley.com/college/strahler/0471669695/interactivities/flash/mineralogy/mineralogy.htm

● Do you want to know more about the importance of minerals? Click this link to read further about the importance of minerals to humans and domestic animals.Soetan, et. al. African Journal of Food Science Vol. 4(5) pp. 200-222, May 2010. The importance of mineral elements for humans, domestic animals and plants: A reviewhttps://www.academicjournals.org/article/article1380713863_Soetan%20et%20al.pdf


http://coolsciencelab.com/mohs_drill.htm

https://www.wiley.com/college/strahler/0471669695/interactivities/flash/mineralogy/mineralogy.htm

https://www.academicjournals.org/article/article1380713863_Soetan%20et%20al.pdf

Check Your Understanding

A. Write true if the statement is correct. Otherwise, write false.

1. A mineral is a naturally-occurring substance. 2. Talc can scratch diamond. 3. A huge mineral has high specific gravity. 4. Bubbles that were formed after pouring an acid to a mineral indicates that

the sample is a carbonate mineral. 5. Quartz is a good example of an idiochromatic mineral. 6. The color of the mineral is always the same as its streak color. 7. Luster is the color of the powdered form of a mineral. 8. Cleavage occurs when the mineral breaks unevenly. 9. Size of the mineral is independent to its specific gravity.

10. Allochromatic minerals are false-colored minerals. B. Identify the odd one among the four options. State also the reason why it is

odd.

A B C D

malachite quartz rhodochrosite sulfur

color solubility streak cleavage

copper cuprite silver gold

basal prismatic cubic dendritic

pearly silky blocky earthy

bornite labradorite malachite opal

PbMoO4 CaWO4 PbCrO4 NaCl

sulfide halides oxides nitrates

melting pt. hardness luster fracture

X-ray fluorescence

wet chemical analysis

inductively coupled plasma

X-ray diffractometry


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C. Give at least two physical properties that you can observe in each of the following minerals.

diamond actinolite copper talc

Challenge Yourself

Answer the following questions. Limit your answer to 2 to 3 sentences.1. You were given two pink minerals (quartz and calcite). Cite ways on how you

could distinguish each mineral.2. Why do you need to check for more than one property in mineral

identification?3. Could water and ice be considered as a mineral?4. Diamond is a very popular mineral used as gemstone. What properties of

these mineral makes it valuable for people?5. If you were given two different mineral samples but does not have any

equipment for hardness test, how would you know which of the two mineral is harder?

6. During an exercise, Josef’s teacher gave him the same mineral shown below: How many cleavage directions are present? What are the approximate cleavage angle directions?


Lesson 6.2: Igneous Rocks


● identify and differentiate the types of igneous rocks; and● describe the origin and environment of formation of igneous

rocks.

The rocks surrounding a campfire do not usually melt. Rocks need very high temperature for it to melt. Igneous rocks that need high rock-melting heat similar to the temperature of the primitive earth. The term igneous comes from the Latin word ignis which means fire. It is formed in temperatures not lower than 700 °C. How can a geologist differentiate one type of igneous rock from the other?

Warm-Up

Crystallize!Materials:

● Four to five sets of colored tags thatcould be worn. (Colored tags aremade from colored papers pasted ona folder. A yarn should be placed toserve as holder for wearing it. Tagsshould be enough so each studentcould have one).

Procedure: 1. Each student should wear the tag

before the game begins.


2. Students should spread out. Make sure each person is as far apart aspossible.

3. After spreading out, a person (it could be your teacher) is assigned to yell “crystallize!”. All students should then look for other students who have the same tags as theirs.

4. After five seconds, the assigned person will yell “stop!”. The students should now stop moving and searching.

5. Count how many members were formed in each set of colored tags.6. Repeat steps 3 to 6 with different time intervals (10, 30, and 60 seconds).

Guide Questions: 1. How many members were formed after the different time intervals?2. What is the relationship of the time interval to the number of members

formed after the time allotted to “crystallize”?3. Based on this activity, what can you infer about the formation of crystals in

rocks?

Learn about It

Minerals such as quartz, feldspar, pyroxene, olivine, amphibole, and mica are the components of almost all types of igneous rocks. Studying this rock type is like studying magma since igneous rocks come from cooled magma. Aside from temperature of the magma, pressure also contributes to the formation of igneous rocks.

Igneous rocks are formed from solidification of magma or lava which flows out from depth. There are two types of igneous rocks based on the temperature-pressure condition during the solidification of magma – extrusive and intrusive. In addition, the time duration is also a factor in the formation of crystals of igneous rocks. Let us deal with this formation and types of igneous rocks in detail.

Formation of Igneous Rocks Igneous rocks are characterized by intergrowth of crystals and/or volcanic glass. Crystal size is an indicator whether a rock is formed deep within Earth or just near the surface. It is directly proportional to the cooling rate of magma. This means that


when the crystals are big, it denotes that the rock is formed deep underground since the magma has a longer trip to the surface giving it longer time to cool down at a very slow rate. On the other hand, magma cools quickly (fast cooling) near the surface that causes formation of smaller crystals since it is given few time to form.

Fig. 18. A model that shows how cooling rate affects crystal size.

An example of a rock with large crystal is a diorite while those with smaller crystals is an obsidian.

diorite obsidian

Fig. 19. Examples of rocks with large crystals.


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Bowen’s Reaction Series Crystals form when magma are cooled. A general model is created to show the progression of silicate crystallization at specific temperature. It is called Bowen’s reaction series which is developed by petrologist Norman L. Bowen.

In the early 1900’s, Bowen comes up with this idea by analyzing what minerals were formed if igneous rocks were subjected to varying temperatures. He started with melting igneous rocks at about 1200 °C. Then, let the magma cool down giving time for crystals to crystallize. After doing it at varying temperature, he found out that there are two different branches. The first one is the discontinuous branch shown at the left side of Fig. 20. The first mineral, olivine, will form if the chemistry of magma (at about 1200 °C) has everything that these minerals need. If the magma is allowed to cool down further, olivine will melt and create pyroxene which is the next mineral in the sequence. Further cooling will form amphibole, and then biotite mica.

On the other hand, the continuous branch does not include the transformation of different minerals. It only shows the development of calcium-rich plagioclase feldspar to its sodium-rich counterpart.

As it proceed down the series, the two branches eventually merge and the magma starts to crystallize into potassium feldspar, muscovite mica, and quartz.


Fig. 20. The Bowen’s reaction series.

Types of Igneous Rocks Igneous rocks can be classified based on the temperature-pressure condition during the solidification of magma: extrusive and intrusive. Extrusive Igneous Rocks An extrusive igneous rock forms when magma or volcanic fragments erupt and solidify on Earth’s surface which results to very fine-grained rock with very small crystals that could not be seen through naked eye. It is also known as a volcanic rock. The texture of most extrusive rocks can be of three different forms: smooth, full of holes, or can be with large crystals embedded in a fine ground mass. Examples of extrusive igneous rocks are obsidian, andesite, and pumice. Obsidian, a rock with a glassy texture, is so smooth because it cools so quick that crystals were not given time to form. Others such as pumice has many holes from escaped gas making this rock so light that it can even float. Some rocks have a porphyritic texture where one mineral is larger than the rest. The larger one is called phenocryst while the remainder is termed as the groundmass. An example of this type are hornblende and andesite. This type of rocks were formed when magma started to crystallize when it is still underneath Earth’s surface (forming phenocryst)


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while others (groundmass) cooled rapidly after the eruption. A hot cocoa with marshmallow can be a good analogy to this porphyritic rocks.

obsidian andesite pumice

Fig. 21. Examples of extrusive igneous rocks.

Intrusive Igneous Rocks An intrusive igneous rock forms when magma crystallizes within the crust and is composed of medium to coarse grains. It is also known as a plutonic rock. Generally, two types of intrusive bodies exist, namely: concordant and discordant type. When the pre-existing rock bed is cut across by an intrusive body, it is termed as concordant while if it runs parallel to the bedrock, igneous rock bodies are called discordant.

Fig. 22. Intrusive igneous bodies.


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As shown in Fig. 22, sills are concordant while dikes and laccolith are discordant. Batholiths are large intrusive bodies formed deep within Earth.

Other Ways of Classifying Igneous Rocks Igneous rocks can also be classified based on their texture and mineral composition. Types of Igneous Rocks Based on Texture Textures of igneous rocks include aphanitic, phaneritic, pegmatitic, vesicular, porphyritic, amygdaloidal, and pyroclastic.

● Aphanitic rock has crystals that are too fine-grained to be seen by the naked eye or even with the help of a hand lens

● Phaneritic rock has grains that are coarse enough to be visible to the eye ● Pegmatitic rock has crystals are greater than 3 cm due to very slow cooling ● Vesicular rock contains tiny holes called vesicles due to gas bubbles in the

lava or magma ● Porphyritic are rocks where larger crystals are embedded in smaller crystals ● Amygdaloidal is when vesicles are filled by low-temperature minerals after

the solidification of magma ● Pyroclastic is formed from the consolidation of individual rock fragments

that are ejected during a volcanic eruption. Types of Igneous Rocks Based on Mineral Composition Classification of igneous rocks based on mineral composition are felsic, intermediate, mafic, or ultramafic.

● Felsic igneous rock is usually light colored and contains large amounts of quartz, potassium feldspar, and plagioclase. It is also called granitic igneous rock.

● Intermediate igneous rock is medium gray or medium green and consists of major minerals like amphibole, plagioclase, and feldspar.

● Mafic igneous rock is dark gray to black-colored and composed largely of plagioclase and amphibole with small amounts of olivine. It is also called as basaltic igneous rock.

● Ultramafic igneous rock has a very dark green to black shade and consists largely of olivine and pyroxene.


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Naming Igneous Rocks Igneous rocks can be named using the binary system which is mainly based on its texture and composition of the rock. This classification is organized using the table below.

Table 9. Classifying igneous rocks based on texture and composition.

Texture

Composition (silica content)

Felsic Intermediate Mafic

extrusive (volcanic) rhyolite andesite basalt

intrusive (plutonic) granite diorite gabbro

Rocks can be classified into extrusive (volcanic) and intrusive (plutonic). Extrusive rocks cool so rapidly that crystals were unable to form. This is the reason for their fine-grained texture. Intrusive rocks, on the other hand, cool so slow. This gives time for the crystals to form making their texture coarse-grained. In terms of composition, felsic is silica-rich while mafic is silica-poor. Intermediate is just in between. A rock with a high silica component is dominated by light-colored minerals and few dark minerals. In contrast, low silica component rocks have more dark-colored minerals than the light ones. Intermediate rocks have equal amounts of light and dark colored minerals. Just by observing these two properties, a person can now name an unknown igneous rock. For example, the unknown rock has few crystals (volcanic) and has more dark-colored minerals than the light ones (mafic). Referring to the table above, the unknown rock is probably basalt.


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Examples

Listed below are the common igneous rocks from pyroclastic eruptions

Table 10. Common igneous rocks from pyroclastic eruptions.

Composition Rock name

felsic rhyolitic tuff

intermediate andesitic tuff

mafic basaltic tuff

Key Points

● Igneous rocks come from the Latin word ignis which means fire. It is formed

from solidification of magma or lava which flows out from depth. ● Igneous rocks can be classified based on the temperature-pressure condition

during the solidification of magma, based on their texture and mineral composition and based on mineral composition.

● Bowen’s reaction series shows the progression of silicate minerals crystallization at specific temperature condition.

● Igneous rocks can be named based on its texture and composition.

Web Links

For further information, you can check the following web links:

● Click on this virtual igneous rock drawer to be familiar with some igneous rocks and test your skills afterwards. Wiley. n.d.. ‘Virtual Rock Lab.’ https://www.wiley.com/college/strahler/0471669695/interactivities/flash/mineralogy/mineralogy.htm


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● Click this site to watch a video on how rocks were formed.KS3 Bitesize -BBC. 2014. ‘Rocks.’http://www.bbc.co.uk/bitesize/ks3/science/environment_earth_universe/rock_cycle/activity/

● Read a journal article about systematically classifying igneous rocks.Le Bas, M. J. and Streckeisen, A. L. "The IUGS Systematics of Igneous Rocks." Journalof the Geological Society 148, no. 5 (1991): 825-833.https://pubs.geoscienceworld.org/jgs/article-abstract/148/5/825/112311/the-iugs-systematics-of-igneous-rocks?redirectedFrom=fulltext


A. Using your knowledge on Bowen’s reaction series, complete the diagram below and answer the questions that follow.


http://www.bbc.co.uk/bitesize/ks3/science/environment_earth_universe/rock_cycle/activity/



https://pubs.geoscienceworld.org/jgs/article-abstract/148/5/825/112311/the-iugs-systematics-of-igneous-rocks?redirectedFrom=fulltext

1. Which mineral in the Bowen’s reaction series has the highest silica content? 2. Which mineral in the Bowen’s reaction has high amounts of calcium and

sodium? 3. Which mineral is the lowest-temperature iron-bearing silicate mineral that

can form a melt? 4. Which minerals contain iron and magnesium?

B. Write the name of the igneous rock based on the description given.

1. high silica content, coarse-grained texture 2. low silica content, fine-grained texture 3. high silica content, fine-grained texture 4. equal amounts of dark and light colored minerals, fine-grained texture 5. low silica content, coarse-grained texture 6. equal amounts of dark and light colored minerals, coarse-grained texture.

C. Identify whether the following igneous rock is intrusive or extrusive.

1. gabbro 2. rhyolite 3. basalt

4. andesite 5. diorite 6. granite

Challenge Yourself

Answer the following questions. Limit your answer in 2 to 3 sentences.

1. By just observing a rock sample, how would you know if it is an intrusive or extrusive rock?

2. You were given two rock samples. One is a dark-colored rock while the other is light-colored. Without using any equipment or chemicals, how could you tell which rock has high silica content?

3. Suggest a way on how an amateur collector can accurately name an unknown igneous rock.

4. In what locations could you most likely find igneous rocks? 5. The mineral olivine and quartz could never be found in the same rock. Why

do you think so? 6. Why some igneous rocks have microscopic crystals while others have large

crystals visible to the naked eye?


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Lesson 6.3: Sedimentary Rocks


● identify and differentiate the types of sedimentary rocks; and● describe the origin and environment of formation of

sedimentary rocks.

A mango graham cake is a favorite of most people who like sweets. In a mango graham cake, graham crackers are at the bottom, then topped with cream and mangoes. After the mango graham cake has been frozen, you will observe distinct layers after you slice it. This cake is a good analogy to sedimentary rocks. The ingredients of the cake are like the sediments that will form layers. These layers are very distinct to sedimentary rocks. What process do sediments undergo to become sedimentary rocks?

Warm-Up

Sedimentary Rocks in a Glass Jar Materials:

● pebbles (marble-sized)● rocks (larger than pebbles)● sand

● soil● water● glass jar

Procedure: 1. At home or at school, collect rocks, pebbles, sand, and soil.2. Get a glass jar. Fill it with the materials you collected at about one-thirds full. 3. Add water and shake it cautiously.4. Predict what will happen and provide reasons why.5. Let the jar undisturbed and watch how the materials settle.


Guide Questions: 1. Based on the activity, why do you think sedimentary rocks are called such?2. What is the difference between the materials that settle on top and at the

bottom?3. If you will reshake the jar, do you think you will still get the same exact

number of layers and position? Why or why not?

Learn about It

Formation of sedimentary rocks requires pre-existing rocks, reserve of sediments, and even fossilized living organisms. These components accumulate on Earth's surface and form sedimentary rocks that exhibit distinctive layering of components.

Formation of Sedimentary Rocks Sedimentary rocks were formed from organic, mechanical, or chemical sediments. A process called lithification is where harden sediments become sedimentary rocks. Sand, silt, and organic material are the components of a lithified soil. In contrast to igneous rocks, the heat needed for lithification is less intense. In addition to heat, compaction and cementation also play a role in this process.

Diagenesis is a collective process where sediments are lithified (becomes rock). It has four main parts: compaction, cementation, recrystallization, and chemical changes (oxidation or reduction).

Compaction As the name implies, compaction is when sediments are smashed together. Imagine a jar with gumballs in it. If there are lots of spaces in between each gumballs, the number is lesser compared when the gumballs are tightly packed within the jar. As more gumballs are added, spaces are lessened and it starts to stick with each other and form one whole mass. Sedimentary rocks also form this way. The accumulated sediments start to be squeezed together. As more and more sediments are deposited, this overlying weight increases. During this process, water present in the sediments is squeezed out.


Cementation After the sediments have been compacted, cementation occurs. Since most sediments can be found in water, water molecules are present in between particles. The various dissolved minerals present in the surrounding water will eventually fall out and attach to the sediment grains. Therefore, cementation acts as glue that binds the particles together.

Fig. 23. Compaction and cementation.


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Crystallization Ions of chlorine, magnesium, potassium, calcium, carbonate, sodium, and sulfate are commonly dissolved in seawater. However, others such as silica and phosphorus which contributes to the make up of sedimentary rock are only found in trace amounts in seawater. These ions will crystallize to form a rock after the water evaporates.

Chemical Changes Biological precipitation of the decayed shells of microorganisms form the carbonate sediments. Through inorganic processes, other calcium-rich and bicarbonate-rich chemical sediments are precipitated as calcium carbonate and carbonic acid. However, these processes are less common.

Fig. 24. Common sedimentary rocks in the Philippines. From left to right: chert, coquina, and limestone.

Remains of plants and animals are also common in sedimentary rocks since the environment of their formation is near Earth’s surface. Sedimentary rocks become more recognizable due to the presence of layers or bedding planes which are formed as sediments settle out and are sorted by transporting agent such as wind or water.

Types of Sedimentary Rocks Sedimentary rocks are classified into clastic or non-clastic.

Clastic Sedimentary Rocks Clastic sedimentary rocks are made up of sediments from preexisting rocks. When preexisting rocks are physically weathered and eroded, they form sediments called clasts or detritus, which are composed of individual minerals or rock fragments. When these sediments are transported, deposited, and lithified, they form the clastic sedimentary rocks. The components of these rocks are called grains if they are minerals and fragments if they are pieces of rocks. In this type of


sedimentary rock, mineral composition is secondary to grain size which means that the sizes of the clasts are essential in its naming and identification. These rocks can be recognized based on their grain sizes that can range from 0.002 mm (e.g. clay size) to > 2 mm (coarse gravel).

When weathering creates clastic sediment, different transporting agents like wind, flowing water, glaciers,organisms, and gravity carry these sediments. Streams carry the largest proportion of clastic sediments, modifying them as they travel downslope. When rubble is carried by a stream for a few kilometers, it becomes rounded due to abrasion or friction. On the other hand, rubble tend to appear angular when they are carried at shorter distances.

The amount and type of sediments a steam can carry depends on its capacity and competence. Stream capacity refers to the amount of sediments it can carry while competence refers to the sizes of the sediments. The speed of a stream affects the size of sediments it can carry. A fast-moving stream can carry large boulders to coarse sediments while a slow-moving stream can only transport fine-grained sediments.

Table 11. Classification of sedimentary rocks based on particle size.

Texture (grain size) Sediment name Rock name

coarse (over 2 mm)

gravel (rounded fragments) conglomerate

gravel (angular fragments) breccia

medium (1/16 to 2 mm)

sand sandstone

fine (1/16 to 1/256 mm)

silt siltstone

very fine (less than 1/256 mm)

clay shale


Non-clastic Sedimentary Rocks Non-clastic sedimentary rocks can be biological, chemical, or a combination of Both.

1. Biological sedimentary rocks are lithified accumulation of dead organisms. Examples include coal (formed from carbon-rich plants) and limestone (formed from the remains of calcareous organisms).

2. Chemical sedimentary rocks form from chemical precipitation. An example

is rock salt formed when dissolved salts precipitate from a solution. This occurs when there is a change in temperature or level of acidity of the solution.

Table 12. Examples of non-clastic sedimentary rocks.

Composition Texture (grain size) Rock Name

calcite

fine to coarse crystalline) crystalline limestone

travertine

shells and cemented shell fragments

coquina

biochemical limestone

shells and shell fragments cemented with calcite cement

fossiliferous limestone

microscopic shells and clay chalk

quartz very fine crystalline chert (light color) flint (dark color)

gypsum dine to coarse crystalline rock gypsum

halite fine to coarse crystalline rock salt

altered plant fragments

fine-grained organic matter bituminous coal


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Examples

The figure below shows an example of how to identify sedimentary rocks.


Key Points

● Sedimentary rocks are formed by the compaction and cementation of sediments, a process called lithification

● Sedimentary rocks are classified into clastic or non-clastic. Clastic sedimentary rocks are made up of sediments from preexisting rocks while non-clastic sedimentary rocks can be biological, chemical, or a combination of both.

● The amount and type of sediments a steam can carry depends on its capacity and competence.

Web Links


● Play this game to master your skill in identifying the age of a fossil. Your goal is to rearrange the order of the layers of sedimentary rocks containing fossils from oldest to youngest.Nesbitt, Sterling. n.d. ‘Layers of Time.’https://www.amnh.org/ology/features/layersoftime/game.php

● Click this link to watch a video on eroded sedimentary rocks in Zambales, Philippines.User:Ponyo Goro. 2013. ‘Sedimentary Rocks Eroded and Visible at Hamat, Sta Rita,Masinloc, Zambales, Philippines.’https://www.youtube.com/watch?v=oH8F_29nurY


https://www.amnh.org/ology/features/layersoftime/game.php

https://www.amnh.org/ology/features/layersoftime/game.php

https://www.youtube.com/watch?v=oH8F_29nurY

https://www.youtube.com/watch?v=oH8F_29nurY


A. Use your knowledge in sedimentary rock identification to complete the diagram below.

B. Complete the crossword puzzle below.


Across 2. Rock made from evaporation

from shallow sea5. Pieces of rock, sand, and silt6. A sedimentary rock formed by

rocks cemented by a mineral

Down 1. Process where breaking down of

rocks into smaller pieces occurs2. Process where sediments are

tightly pressed together.3. Process where crystallization of

dissolved minerals and bindingthe sediments together happens.

4. A natural cement that acts as aglue to hold together sediment.

Challenge Yourself

Answer the following questions. Limit your answer in 1 to 2 sentences. 1. How can you distinguish an igneous rock from sedimentary rocks?2. Your history teacher asked you to show something that can give idea of the

information about the primitive Earth. Is presenting a sedimentary rock satisfy this requirement given by your teacher? Why or why not?

3. Why is water essential to form caves?4. Provide an explanation why the rigid components of plants and animals are

more likely preserved on the rocks compared to the softer components.5. How could you accurately predict that the unknown rock sample is

sedimentary rock? What features are you looking for?


Lesson 6.4: Metamorphic Rocks


● identify and differentiate the types of metamorphic rocks; and● describe the origin and environment of formation of

metamorphic rocks.

Witnessing a butterfly metamorphosis where a caterpillar becomes butterfly is a wonderful thing to witness. Metamorphosis is a Greek word which means “to change form”. Like this butterfly, rocks can also metamorphose. It can be a previously igneous or sedimentary that changed into metamorphic rock. How do rocks change its form?

Warm-Up Metamorphic Crayons Materials:

● shaved pieces of crayons● plastic medicine cup● alcohol lamp or microwave● hammer

Procedure: 1. Cut or shave pieces of different colors of crayons.2. Layer each color of crayons in a plastic medicine cup.3. Apply pressure using your thumb.4. Put more pressure by using a hammer.5. Put the medicine cup with layers of crayons (pressure applied) inside a

microwave oven for about 2 minutes. Make sure that it will not melt completely. You may also melt it using an alcohol lamp or any source of heat.


6. Let it cool before you popped it out of the cup. You now have a model of metamorphic rock.

Guide Questions:

1. What are the forces that you applied to make a metamorphic rock? 2. Igneous and metamorphic rock are formed by subjecting it to heat. If they

are both subjected to high temperatures, why are these rocks still appear different?

Learn about It

Metamorphic rocks are rocks that have been altered, changed, or transformed in the solid state due to changes in pressure, temperature conditions, and chemical actions of hot fluids. Formation of Metamorphic Rocks Metamorphism is like the chameleon changing its color to protect itself by blending into its environment. The goal of metamorphism is like the chameleon which is to reestablish equilibrium with the new conditions. Ways on How Metamorphism Can Happen Changes in minerals during metamorphism can happen in three possible ways. These are recrystallization, neomorphism, and metasomatism.

1. In recrystallization, small crystals of one mineral will slowly convert to fewer, larger crystals of the same mineral without melting the rock.

2. Neomorphism is the process whereby minerals not only recrystallize, but also form different minerals from the same chemical elements

3. Metasomatism is the addition or loss of elements new minerals form with only some of the original elements, and new elements were added through hydrothermal migration. Example is the transformation of limestone to marble.


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Types of Metamorphism The scale indicating the level of pressure and temperature during the formation of a particular metamorphic rock is called metamorphic grade. The higher the temperature and pressure, the higher the metamorphic grade is. There are two main scales at which metamorphism can occur: contact and regional metamorphism.

Contact metamorphism occurs only at a local area adjacent to large intrusions and along fractures that are in contact with hot fluids. Contact metamorphism is most effective at narrow zones specifically at the contact between the host rock and intrusive magma or hot fluids.

Regional metamorphism occurs at very large areas for example mountain ranges which results from the following conditions:

● Metamorphism may occur when there are major igneous intrusions that form and cool over long periods of time.

● Another condition that may result to metamorphism is the presence of extreme pressure and heat due to deep burial or tectonic movements of rock.

● Lastly, regional metamorphism may happen when there is a widespread migration of hot gases or condensation throughout a region.


Types of Metamorphic Rocks Metamorphic rocks can be classified as foliated or nonfoliated based on texture. Foliated Metamorphic Rocks Foliated metamorphic rocks are formed when parallel planes of platy or elongated minerals were realigned due to the effects of pressure and recrystallization creating what is called as foliations. Examples of foliated metamorphic rocks are schist, gneiss, and phyllite.

Fig. 28. Increasing metamorphism causes distinct bands or foliation to form.

Nonfoliated Metamorphic Rocks Nonfoliated metamorphic rocks do not have layered appearance. Examples are marble, quartzite, and anthracite. Foliated and nonfoliated metamorphic rocks can be further classified based on their parent rocks or protolith. Protoliths for metamorphic rocks can be any type of rock, whether igneous, sedimentary, or even metamorphic. However, such classification or identification of protolith can be difficult because of the rock alteration during metamorphism. Fig. 29 shows the parent rocks of different foliated and nonfoliated rocks.


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Fig. 29. Some metamorphic rocks with their corresponding protoliths.

Fig. 30. Common metamorphic rocks in the Philippines. From left to right: marble, mica schist, and slate.

The Rock Cycle The rock cycle shows that all rocks are related to each other. Igneous rocks can change into sedimentary or metamorphic rocks. Sedimentary rocks may also transform into igneous or metamorphic rocks. Metamorphic rocks, on the other


hand, can change into the all the three rock types. All these changes, of course, are only possible if the ideal conditions and processes needed are met. The arrows found in the figure represent processes in each group especially the role of various geologic processes involved in the transformation of one rock type into another.

Fig. 30. Transformation of igneous, sedimentary, and metamorphic rocks.


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Classifying Igneous, Sedimentary, and Metamorphic Rocks To identify an unknown rock sample, just follow this key shown below for you to be guided on classifying the rock sample in an accurate manner.

Fig. 31. Classifying rock types.

Key Points

● Metamorphic rocks are rocks that have been altered, changed or

transformed in the solid state due to changes in pressure, temperature conditions and chemical actions of hot fluids.

● Recrystallization, neomorphism, and metasomatism are the three possible ways where changes in minerals during metamorphism can happen.

● Metamorphic grade is a scale indicating the level of pressure and temperature during the formation of a particular metamorphic rock.


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● Contact metamorphism and regional metamorphism are the two main scales at which metamorphism can occur.

● Metamorphic rocks can be classified as foliated or nonfoliated based on texture

● The rock cycle shows that all rocks are related to each other.

Web Links


● To master your skill in identifying and describing each type of rocks, try this interactive activity. Anneberg Foundation. 2017. ‘Interactives - Rock Cycle.’ https://www.learner.org/interactives/rockcycle/identifyrock/

● Try this “Who Am I Rock Game” to practice your skill in identifying specific characteristics of each type of rock. Kids Geo. 2018. ‘Identify Rocks Game.’ https://kidsgeo.com/geology-games/identify-rocks-game/

● Do you want to read further on metamorphic rocks found in the Philippines? Read this article entitled “Petrography of metamorphic rocks in northwestern Mindoro, Philippines: Preliminary results.” Aldea, et. al. "Petrography of metamorphic rocks in northwestern Mindoro, Philippines: Preliminary results (Abstract)." Earth Sciences International Conference, Philippines. p. 91. http://rwg-tag.bravehost.com/Conferences/ESIC_Posters.pdf


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https://www.learner.org/interactives/rockcycle/identifyrock/

https://kidsgeo.com/geology-games/identify-rocks-game/

http://rwg-tag.bravehost.com/Conferences/ESIC_Posters.pdf


Complete the crossword puzzle below.

Across 4. This diagram shows

that one rock is a rawmaterial for another.

7. Type of metamorphicrocks that do not havelayered appearance.

Down 1. Also called as parent rock.2. Has the highest metamorphic grade.3. A type of metamorphism that occurs at very

large areas.5. A type of metamorphism due to contact with

magma or igneous intrusion.6. Type of metamorphic rock formed when

parallel planes of platy or elongated mineralswere realigned due to effects of pressure andrecrystallization.


Challenge Yourself

Answer the following questions. Limit your answer in 2 to 3 sentences.

1. What do you mean by the statement, “One rock is the raw material for the other?”

2. What is the difference between regional and contact metamorphism? 3. How do you distinguish metamorphic rock from the other two types?


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Laboratory Activity

Activity 6.1 Rock Sample Classification

Objectives At the end of this laboratory activity, the students should be able to:

● identify rocks by using various classification test; and● familiarize how each classification tests is done.

Materials and Equipment ● nail● vinegar● penny● plastic cup

● ceramic tile scraps● magnet● six different rock samples

Procedure Test 1. Hardness test

1. Scratch one rock at a time to the following objects:a. fingernail = 2.5b. penny = 3.0c. nail = 5.0

2. Write your observation on the table provided.3. Arrange your samples from softest to hardest.

Test 2. Color streak test 1. Get your rock sample and make a streak on the ceramic tile scrap.2. Write your observation on the table provided.

Test 3. Acid test 1. Pour vinegar to your plastic cup. Fill it up to half of the cup.2. Put your rock sample inside the cup.3. Observe bubbles that will form. Write your observation on the table

provided.


Test 4. Magnetism test 1. Obtain one rock sample at a time and touch it with a magnet. 2. Observe if the rock will be attracted by the magnet. 3. Write your observation on the table provided.

Data and Results Table 1. Rock Sample Classification Tests

Rock Sample No. 1 2 3 4 5 6

Hardness test

Color streak test

Acid test

Magnetism test

Guide Questions 1. How can you tell whether the rock sample is harder than the other rocks?2. Is the streak color always the same as the rock’s color?3. What can you say about the composition of a rock if it is attracted by a

magnet?

Performance Task

Rock CD Cover

Goal ● Your task is to make a rock and rap CD

album.

Role ● You have been asked to make a CD album

consisting of five parts: Band name and CD cover design, chosen rock band’s biography, names of band members, list of songs, and rock cycle diagram.


Audience ● Your clients are your customers and fans (classmates and teachers).

Situation ● The context you find yourself in is as a rock band member.

Product, Performance, and Purpose ● You will create your own type of rock band that you would like to

be—igneous, metamorphic, or sedimentary and write your band biography. Make sure that band member names and songs are still within the theme of your rock type. All of these criteria should be met in order to attract customers to buy your CD album.

Standards and Criteria for Success ● Your performance will be graded by the following rubric.

Criteria Below Expectations, 0% to 49%

Needs Improvement

50% to 74%

Successful Performance 75% to 99%

Exemplary Performance

100%

Content. Detailed facts are presented well. Content related to the task.

Details not presented. Content is not related to the task.

Details are presented but not organized. There are some content that are not related to task.

Details are presented in an organized manner.Content are related to the task.

Details are presented in an organized matter that can be easily understood. Content are related to the task. Additional supporting details are presented.

Performance and Presentation. Presentation was done in a clear and logical manner.

Performance was not done. There was no album presented.

Performance was done but in a disorganized and illogical manner.

Performance was done smoothly but the concepts are presented in such a way that should be rearranged for better understanding.

Performance was done clearly. Concepts were presented in a logical manner and easily understandable by the audience.

Musicality The performance has a very poor tone quality and intonation.

The performance has minor flaws for tone quality and intonation.

The performance has good tone quality and intonation.

The performance has excellent tone quality and intonation.


Self Check

After studying this unit, can you now do the following?

Check I can…

differentiate the types of rocks.

identify how each type of rock is formed.

cite important minerals and rocks to society.

Key Words

Cementation It happens when the dissolved minerals are deposited in the spaces between the sediments and acts as glue that binds the particles together.

Compaction It occurs when the sediments are squeezed together caused by the overlying weight of other sediments.

Igneous rock These are formed from magma or lava and volcanic fragments.

Metamorphic rock These are are formed when rock types recrystallize in response to elevated temperature-pressure conditions.

Metamorphism It involves change in mineral assemblage and texture.

Mineral It is the building blocks of rocks. They are naturally occurring, inorganic, solid material that has a fixed structure and a definite chemical composition.

Rock It is a naturally-occurring aggregate of one or more minerals and may contain mineraloids, organic matter and pre-existing rocks.

Sedimentary rock These are rocks formed when sediments are lithified.


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Wrap Up

Identifying Minerals and Rocks

Photo Credits

Fig. 1. Rhodochrosite by Tony Hisgett is licensed under CC BY 2.0 via Wikimedia commons;Malachite by Anagoria is licensed under CC BY-SA 3.0 via Wikimedia commons; Sulfur by Daniel Schwen is licensed under CC BY-SA 2.5 via Wikimedia commons.

Fig. 2. Colorless quartz by Eurico Zimbres is licensed under CC BY-SA 2.5 via Wikimedia commons; Milky quartz by Anonymous via Wikimedia commons; Rose quartz by Feezo is licensed under CC BY-SA 3.0 via Wikimedia commons; Citrine quartz by Rama is licensed under CC BY-SA 3.0 via Wikimedia commons; Smoky quartz by Dario Crespi is licensed under CC BY-SA 3.0 via Wikimedia commons; Amethyst by Didier Descouens is licensed


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under CC BY-SA 3.0 via Wikimedia commons. Fig.3. Bornite by Parent Gery is licensed under CC BY-SA 3.0 via Wikimedia

commons; Labradorite by Anonymous via Wikimedia commons; Precious opal by Rob Lavinsky is licensed under CC BY-SA 3.0 via Wikimedia commons.

Fig.5. Talc by Rob Lavinsky is licensed under CC BY-SA 3.0 via Wikimedia

commons; Dioptase by Rob Lavinsky is licensed under CC BY-SA 3.0 via Wikimedia commons; Pyrite by Battistini Riccardo is licensed under CC BY-SA 4.0 via Wikimedia commons; Diamond by Henry Li is licensed under CC BY-SA 3.0 via Wikimedia commons; Microcline feldspar by Zimbres is licensed under CC BY-SA 2.0 via Wikimedia commons; Azurite by Parent Gery is licensed under CC BY-SA 3.0 via Wikimedia commons; Chrysotile by Zimbres is licensed under CC BY-SA 2.5 via Wikimedia commons.

Fig. 6 Copper by Anonymous via Wikimedia Commons; Oligoclase by Rob

Lavinsky is licensed under CC BY-SA 3.0 via Wikimedia commons; Natrolite by Didier Descouens is licensed under CC BY-SA 4.0 via Wikimedia commons; Indicolite by Parent Gery is licensed under public domain via Wikimedia commons; Okenite by Anonymous via Wikimedia commons; Barite by Anonymous via Wikimedia commons; Actinolite by Rob Lavinsky is licensed under CC BY-SA 3.0 via Wikimedia commons.

Fig. 8 Muscovite by Rob Lavinsky is licensed under CC BY-SA 3.0 via Wikimedia

commons; Augite by Rob Lavinsky is licensed under CC BY-SA 3.0 via Wikimedia commons; Hornblende by Lamiot is licensed under CC BY-SA 4.0 via Wikimedia commons; Halite by Zell is licensed under CC BY-SA 3.0 via Wikimedia commons; Calcite by Siim is licensed under CC BY-SA 3.0 via Wikimedia commons; Fluorite by Carles Millan is licensed under CC BY-SA 3.0 via Wikimedia commons; Sphalerite by Rob Lavinsky is licensed under CC BY-SA 3.0 via Wikimedia commons

Fig. 9. Obsidian by Ivtorov is licensed under CC BY-SA 4.0 via Wikimedia commons;

Copper by James St. John is licensed under CC BY-SA 2.0 via Wikimedia commons; Kyanite by Rob Lavinsky is licensed under CC BY-SA 3.0 via Wikimedia commons.

Fig. 19. Diorite by Rojinegro81 is licensed under CC BY-SA 3.0 via Wikimedia


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commons and Obsidian by Anonymous via Wikimedia commons.

Fig. 21. Pumice by Lassen is licensed under CC BY-SA 2.0 via Wikimedia commons and Andesite by James St. John is licensed under CC BY-SA 2.0 via Wikimedia commons

References

Amethyst Galleries Inc. “Mineral Gallery” Accessed April 5, 2018. http://www.galleries.com/default.htm

Coenraads, Robert R. 2005. Rocks & Fossils: A Visual Guide. Australia: Weldon Owen Inc.

Tarbuck, Edward J. and Frederick J. Lutgens. 2012. Earth Science, 13th Edition. New Jersey: Pearson Prentice Hall.

Thompson, Graham R. and Jonathan Turk. 1997. Introduction to Physical Geology. United States: Brooks Cole Publishing.

Williams, Linda. 2004. Earth Science Demystified. United States: The McGraw -Hill Companies, Inc.



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