Roser Canet_3r ESO_materials on the Earth Crust

UNIT 1 – MATERIALS ON THE EARTH

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...........

MATERIALS ON THE EARTH’S CRUST

The Earth crust is the outer layer of our planet. It covers

the whole Earth surface. The thickness of this layer varies from 6 to 12 Km on the seabed to up 60 Km in the great

mountain ranges. The Earth crust is made up of rocks which in turn are

made up of minerals. There are many different types of minerals. Diamond rings, talcum powder, and aluminum

foil are made from minerals. Copper wire, china dishes,

and table salt are also made from minerals. What do all minerals have in common?

http://geology.about.com/od/mineral_ident/ss/beginmini

dent_4.htm

Minerals are solid materials of Earth’s crust. Minerals are

made of chemical elements. Some minerals are made of one element (atom). Each kind of atom is represented by

a symbol. Gold (Au), silver (Ag), copper (Cu), and carbon(C) are minerals made of one element.

Most minerals are chemical compounds. Chemical compounds are two or more elements joined together

(molecules). Each mineral has chemical composition. Scientists classify minerals by their chemical composition.

http://geology.about.com/od/mineral_ident/ss/beginminident_4.htm

http://geology.about.com/od/mineral_ident/ss/beginminident_4.htm


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ACTIVITY

- Read the text and make a graphic bar about the three most abundant elements in the universe and in the Earth.

The most abundant element in the universe is hydrogen

(H), which makes up about 3/4 of all matter! Helium (He)

makes up most of the remaining 24%. Oxygen (O) is the third most abundant element in the universe. All of the

other elements are relatively rare.

The chemical composition of the Earth is quite a bit

different from that of the universe. The most abundant element in the Earth's crust is oxygen (O), making up

46.6% of the Earth's mass. Silicon (Si) is the second most abundant element (27.7%), followed by

aluminum(Al) (8.1%), iron(Fe) (5.0%), calcium(Ca) (3.6%), sodium(Na) (2.8%), potassium(K) (2.6%). and

magnesium(Mg) (2.1%). These eight elements account for approximately 98.5% of the total mass of the Earth's

crust.

Find out the four most abundant elements in living

things. Which are the same and which are different from

the most abundant elements in universe and in Earth crust?

GRAPHIC BAR


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Atoms and molecules make patterns when minerals form. These patterns cause minerals to make shapes called

crystals. When minerals have time and space they can grow into beautiful forms or shapes.

Diamond crystal structure

Hexagonal crystal

Some words to describe different crystal shapes are:

cubic : equal, square faces dendritic : branching, tree-like, looks like the

veins in a leaf or like a painted “tree shape” dog-tooth : shaped like the canine tooth, like a

dog's tooth fibrous : looks like fibers, threads, parallel lines

geode : spherical, round shape that is hollow inside, often lined with crystals

prismatic: like a prism with flat ends, longer than it is wide.

rose shaped : looks like a flattened flower or rose with petals


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ACTIVITY

Find out the composition of graphite and diamond. Explain why they have different properties.

ACTIVITY

Are the following minerals? Give reasons for your answer. a) Water

b) Zirconia (artificial diamond) c) Coral

………………… (is/is not) a mineral because it

………………… a)

b)

c)

ACTIVITY (make questions) Put the words in the right order to make interrogative

sentences: a) living things/formed by/minerals/Are?

b) the same/ Does/ chemical composition/ always/ have/a mineral?

c) have / How many/does/elements/gold?

d) minerals/to grow/What/into crystals/do/need?


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PROPERTIES OF MINERALS

Colour

Colour is one of the physical properties most commonly

used to describe minerals, but it is not a very good property to use to identify minerals.

Some minerals are nearly always the same color like azurite (blue) and sulfur (yellow) but many minerals

come in a variety of colors – the changes are caused by slight chemical impurities or through exposure to heat,

moisture and air. Some minerals have common names to describe a

specimen with a certain colour. eg. Quartz – rock crystal (colorless), smoky quartz

(brown), citrine (yellow), amethyst (violet), rose quartz (pink).

Lustre

Lustre describes the way light reflects off of the surface of a mineral. We can describe it as metallic (very shinny like

metals such as pyrite, gold or silver) or non-metallic.


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!!! There are different words to describe non-metallic

luster: dull/earthy, waxy (like the surface of a candle), greasy /oil, pearly, silky (like a piece of cloth),

glassy/vitreous (looks like a glass), resinous, adamantine (like a diamond).

Streak

If you rub a mineral against a streak plate you will get a powder. The color of this powder is called streak. A

mineral can come in different colors but its strake is always the same. A mineral’s strake may be different

from its outer colour. Pyrite looks like gold from the outside but it has a green strake.

Hardness

Hardness is how difficult is to scratch a mineral. Soft minerals are easily scratched. Mohs scale of hardness

shows how hard a mineral is. Talc is number 1.It is the softest. Diamond is number 10.It is the hardest. Every

item on the list can scratch something above it.

Scratching tools:


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fingernail (2.2)

copper penny (3.5) pocket knife (5.2)

piece of glass (5.5) steel file (7.5)

piece of corundum (9)

Rating Description Mineral Example

1 Very Soft Can be scratched

with a fingernail Talc

2 Soft Can be scratched

with a fingernail Gypsum

3 Soft Can be scratched

with a copper penny Calcite

4 Semi-Hard Can be scratched

with a common nail Fluorite

5 Hard

Can be scratched

with a common nail

(5.2).

Apatite

6 Hard

Mineral of hardness

6 or more will

scratch glass.

Feldspar

7 Very Hard Can be scratched

with a concrete nail Quartz

8 Very Hard Topaz

9 Extremely Hard

Used in industrial

tools for cutting,

grinding & sanding.

Corundum

10 The Hardest Diamond is used to

cut all minerals

including diamonds.

Diamond

ACTIVITY

Show the approximate value of hardness in the following

minerals: - Pyrite: It scratches fluorite but it doesn’t scratch

feldspar. - Silver: It scratches gypsum but it doesn’t scratch

fluorite.

Invent two sentences comparing the hardness of two minerals. Use the pattern given above.

-

-


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ACTIVITY (Comparatives)

Gypsum is ………………. (soft) than …………………………. The ……………………….. ( hard ) mineral is…………………….

Topaz is ………………….. (hard ) than quartz. The ………………. (soft ) mineral is talc.

Cleavage

When a mineral breaks with smooth flat surfaces.

Cleavage can be described as perfect, good, imperfect, poor. Galena breaks into cubes and mica breaks into

sheets.

The flat surfaces of these minerals tend to break. Many minerals do not break smoothly. They have fracture when

they break. Words that describe what a break in a rock or mineral looks like:

conchoidal : curved break like what happens with thick glass or bottle bottom, shell shaped,

can be rough or smooth splintery : fibrous

uneven : rough surface, not smooth

Specific Gravity (or density) indicates how many times

more the mineral weighs compared to an equal amount of water.

Some minerals are denser than others. They have a lot of mass packed into a small volume. High density makes

a mineral very heavy. Gold, silver, and galena are dense minerals. Gypsum and halite are light minerals.

Magnetism

Some minerals have special properties. Magnetite is


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attracted by a magnet.

Taste can also serve to identify minerals. Halite tastes

salty.

Transparency is the ability to transmit light. Minerals

can be transparent, translucent or opaque.

Fluorescence is the ability to emit visible light when a mineral is exposed to ultraviolet light.

Double refraction or Birefringence is the decomposition

of a ray of light into two rays when it passes through a

material. Many minerals are able to decompose light into two rays but we are able to see it in transparent calcite.

LABORATORY PRACTICE-2

PHYSICAL PROPERTIES OF MINERALS

Material:

You will be given different boxes that contain different elements to solve problems. Before beginning the activity

check the contents of each box. If something is missing, please tell the teacher.

Problem 1 (Study of hardness): talc, gypsum, calcite, quartz, corundum, metal screw, a piece of

glass.

Problem 2 (Study of magnetism): pyrite, magnetite,

calcite, a magnet.

Problem3 (Study of cleavage): muscovite (mica), limonite, gypsum, calcite, galena.


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Problem 4 (Study of fracture): quartz, jasper,

fibrous gypsum, asbestos.

Problem 5 (Study of colour in monochromatic minerals): azurite, malachite, sulfur, graphite.

Problem 6 (Study of colour in alochromatic minerals): white, yellow, rose, green and smoked

quartz, green and violet fluorite.

Problem 7 (Study of streak): limonite, hematite, cinnabar, magnetite, a piece of porcelain.

Problem 8 (Study of density): barite, quartz, cylinder, balance.

Problem 9 (Study of luster): galena, pyrite,

sphalerite, fibrous gypsum, quartz.

Problem 10 (Study of taste): silvine, halite, talc

and a cellulose paper to dry out.

Problem 11 (Study of birefringence): transparent calcite (Iceland spar).

Problem 12 (Study of mineral habits): gypsum in rosette habit, gypsum in bladed habit, aragonite

crystals, pyrolusite in dendritic habit, quartz in

geode.

Problem 13 (Study of fluorescence): fluorite.


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HOW DO MINERALS FORM?

Minerals have different origins.

Magma is a mixture of molten rocks deep under the Earth surface. It is very hot. Some minerals form when magma

cools .The molecules in magma move very fast. The molecules slow down when magma cools. Then the

molecules form crystals. The magma hardens. It becomes

a solid. Sometimes magma takes a long time to cool. The crystals have more time to grow and they get very large.

Some minerals form deep in Earth. It is hotter deep in Earth. Rocks on top press the rocks underneath. The heat

and the pressure produce minerals. When the crust moves these minerals move to the surface.

Other minerals form when water cools. Magma heats

water deep in the earth. This water has lots of dissolved minerals. When water cools, minerals become crystals

and they fall to the bottom of the water.

Minerals can also form when water evaporates. Ocean water contains many dissolved minerals. The ocean water

evaporates and crystals are formed. The salt you use on

food comes from the ocean.

ACTIVITY Make a picture about four methods minerals are formed.

HOW DO PEOPLE USE MINERALS?

ACTIVITY (internet)

Diamonds, sapphires and rubies are gemstones. People

like them because they are rare and beautiful. They make jewelry with them. Use the internet to learn more about

gemstones. Write a text in your own words about your favourite gemstone.

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

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_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _

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- Some useful minerals are called ores. An ore is a mineral that contains a substance people can use. Iron

comes from hematite. People use iron to make nails, buildings, and ships. Aluminum comes from bauxite.

Aluminum is lightweight. People use it to make foil, cans, and jets. Iron and aluminum are metals. Metals help

electricity to flow. People can stretch metals into wires.

ACTIVITY (internet) Copper and magnesium are also metals. How do people

use them? Which minerals do they come from?

ACTIVITY (at home) Do a research at home. Make a list of at least 3 minerals

you can find in the kitchen, in the bathroom and in your bedroom.


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HOW ARE ROCKS ALIKE AND DIFFERENT?

A rock is formed by one or more minerals. If you look at granite, you can see crystals of quartz (white), feldspar

(pink), mica (black), and hornblende (black). Sometimes the crystals are too small to see.

As we have studied, each mineral has its own properties. A rock with several minerals has a mixture of properties.

We can identify a rock by its minerals but also by its colour (light or dark- coloured), density and texture.

Texture refers to the kind of grains: coarse, large, fine,

small, with smooth edge or jagged edge… A rock’s colour, density and texture depend on how the rock formed.

ACTIVITY

Describe the following rocks according to the colour and the kind of grains.

1. Basalt

2. Granite


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1. _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _

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2. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

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_ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

_ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Geologists classify rocks according to their


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origin into the following three groups:

Igneous, sedimentary and metamorphic.

WHAT ARE IGNEOUS ROCKS?

All rocks start below Earth´s surface. They are molten, or melted, deep under the surface. You already know that

molten rock under the surface are called magma. Magma

is less dense than material around, so it rises to the surface. Sometimes, magma cools before reaching the

surface. It hardens into rock. When magma cools and hardens an igneous rock form. When magma reaches

the surface without cooling, we call it lava. Lava forms igneous rocks when it cools and hardens on the surface.

Magma cools slowly below ground. Crystals take a long time to grow. They become coarse, or large. Lava cools

quickly above the ground. Crystals are smaller. Sometimes lava cools so quickly that no crystals form.

ACTIVITY Look again at the granite and the basalt. How are their

crystals? Where do you think they were formed?

Rocks that cooled above ground are called extrusive or volcanic. They often have cavities in them, produced by

gas. These are called bubbles or vesicles (holes). Rocks that are cooled below ground are called intrusive.

ACTIVITY (internet)


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Obsidian and pumice stone are igneous rocks. Look for a

picture of them, say if they are extrusive or intrusive and justify your answer.

WHAT ARE SEDIMENTARY ROCKS?

- Sedimentary rocks are made of bits of sediment joined together. Sediment may be pieces of weathered rock,

shells, or the remains of organisms. Water, wind, and ice

move sediment from a place to another. They deposit sediment. The sediment drops and makes layers.

Sedimentary rocks form when sediment is compacted and

cemented together. The layers of sediment are heavy.

The top layers squeeze the bottom layers. Bits of minerals “glue” coarse sediments together. This happen

because water with dissolved minerals squeezes between coarse pieces of sediment. The water evaporates and

mineral crystals form. The crystals hold the pieces of sediment together. The sediment becomes a rock.

Weathering, the first step to a “second hand” rock


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We often find places like this around mountains:

a)

These piles of broken rock are called scree. The kinds of changes that break up rocks are called weathering

processes. In limestone areas we can find caves with a lot of pointed

stalactites and stalagmites. This is caused by rain-water

which is very weak acid. As it falls, it takes carbon dioxide from the air and becomes very weak carbonic acid.

b)

Physical weathering is caused by expansion effects due to

temperature changes or be due to freezing of water in


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cracks. Chemical weathering is caused by reactions

between the minerals in the rock and the environment. Match a) and b) to physical and chemical weathering

processes.

Second step: The bits of rock must move to a new home.

The bits of rock will be likely to go down because of gravity. To make them move they also need energy. The

energy can come from various agents. One of the most important agents is water. Rivers, for example. But

water isn’t the only way of carrying the bits. The wind is also an agent. Ice can move rock, too. All these

processes cause erosion-which means actually removing from its original place. In nature, sediments that travelled

a long way are usually sorted and rounded.

ACTIVITY

Which of the next is made of sediment that travelled a long way? Which is made of sediment that travelled a

short distance? Explain it.


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Sedimentary rocks often hold evidence of how the bits

that make them were transported. Usually, the more

transport, the more energy has affected the bits. They become rounded and more sorted.

The greater the energy in the process, the bigger the bits

that can move. When the energy gets less, the bigger bits drop first. Sediment turns to rock slowly by squeezing

under its own weight and by cementing by natural chemicals. Hard minerals (like quartz) resist rounding

more than soft minerals (like calcite).

ACTIVITY

To make the list of the things that must happen to make a rock from pebbles of older rocks, let’s fill in the gaps

the next sentences using the verbs given below in the

right order: First the original rocks must get …………………. Then the

bits must get ……………………to the place where we find them. They often get …………………….They get ……………………

together. They get …………………… together. CARRIED (carry); ROUNDED OFF (round); STUCK (stick);


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DROPPED (drop); BROKEN UP (break)

Examples of sedimentary rocks:

We classify the rocks according to the sediment size or the material they are made of.

The sediment can be from small to large: clay, silt, sand or gravel. The rocks are called:

Clay Shale______

Silt Siltstone____

Sand Sandstone___

Gravel Conglomerate

Some sedimentary rocks are made of crystals that were dissolved. When water evaporated, the rock formed. This

is how halite, the rock salt, forms.

Limestone forms when water with calcite evaporates. Some sedimentary rocks are made of material from

organisms or by organisms.

Coquina is made of shells cemented together and Coral

limestone is made of coral skeletons.

Bituminous coal is a sedimentary rock formed millions of years ago from dead plants buried in swamps and forests.

People use it for energy.

Sedimentary rocks tell us about Earth’s history. They often have fossils. Fossils are the remains or imprints of

organisms from the past. Sometimes the remains of dead organisms were covered with mud, and other sediments.

The sediment, the imprints, and the remains hardened over time and became rock.

ACTIVITY


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Almost all fossils are found in sedimentary rock. Why do

you think fossils cannot be found in igneous rock?

ACTIVITY (internet)

Find out information about the origin of petrol. Write it

down in your own words in four sentences.

WHAT ARE METAMORPHIC ROCKS?

There are high temperatures and a lot of pressure deep underground. Heat and pressure change rocks. A rock

formed by heat and pressure from another rock is called

metamorphic rock. This is what happens.

Sometimes a rock deep underground does not melt. It stays solid.

The mineral grains in the rock may flatten and line up. The minerals in the rock may change their chemical

composition. The minerals in the rock may separate into layers of

different densities. - Each of these things makes a new rock.

Original rock Metamorphic rock

Granite Gneiss

Shale Slate Sandstone Quartzite

Limestone Marble

Slate Schist

ACTIVITY


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Classify the “original rocks” above into the group they

belong to. Which kind of rocks can transform into metamorphic

rocks?

ACTIVITY Metamorphic rocks have useful properties. For example,

slate is impermeable and breaks into layers. What is it used for?

Marble is shinny and colourful. It is easy to carve. What do people use it for?

THE ROCK CYCLE

Rocks come from other rocks. Rocks change from one rock to another. Sedimentary rocks are made of broken

pieces of rock. Igneous rocks come from magma or lava. Metamorphic rocks come from any rock subjected to high

pressure or high temperature. The process of rocks changing is called rock cycle.

Weathering is part of the rock cycle. Remember that

weathering is breaking rocks into bits and pieces.

ACTIVITY (internet)

Click on this web and do the exercices.

www.learner.org/interactives/rockcycle/index.htlm

ACTIVITY

http://www.learner.org/interactives/rockcycle/index.htlm


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Make a diagram about the sequence of events that

happen to rocks into the rock cycle. Use the following words: weathering, cooling and crystallizing, melting,

compaction and cementation, sediments, deposition, transportation, consolidation…

Sedimentary rocks

Metamorphic rocks Magma

Sediments

Igneous rocks

ACTIVITY (internet) To finish, search the main kind of rocks we can find in

Catalunya. The four basic areas are: granite and metamorphic areas, calcareous areas, clay areas and

volcanic areas. Identify them and paint the following

map:

LABORATORY PRACTICE 1

Experiment with malachite


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Material:

Some malachite specimens, test tubes, water, limewater, hydrochloric acid solution, iron nail, rusty nail, fresh nail,

Bunsen, tongs, collection of metals.

Method:

Put some malachite in a clean test-tube. Add a few drops of water.

- Does the malachite dissolve easily in water? Put some limewater in another tube.

Add a few drops of dilute hydrochloric acid to the malachite. Shake the limewater gently.

- What happens to the malachite?

- What happens to the limewater? Explain. Drop more acid into the malachite until no malachite is

left. Describe the “malachite tube” until no malachite is left.

Now take a clean iron nail. Drop the nail into the test-tube that had the malachite in it and leave it for a few

minutes. Take out the nail. Describe what has happened to it.

Compare it with a rusty nail and a fresh nail. Put all three in a Bunsen flame, using tongs. What do you see?

Break all three nails. What do you see? Compare the nail you left in the “malachite solution” with

a collection of different metals. Which metal has come out of the malachite?

You have now found TWO materials that can come out of

malachite. What are they? One is a gas, one a metal. Were they similar in

appearance to the malachite?

Now you should be able to see why we say minerals are usually COMPOUNDS. They are made of other things

chemically compounded together, and they can be taken apart again if we use the right chemical methods.


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LABORATORY PRACTICE 2 Physical properties of minerals

Material:

You will be given different boxes that contain different elements to solve problems. Before beginning the activity

check the contents of each box. If something is missing,

please tell the teacher. Problem 1 (Study of hardness): talc, gypsum,

calcite, quartz, corundum, metal screw, a piece of glass.

Problem 2 (Study of magnetism): pyrite, magnetite, calcite, a magnet.

Problem3 (Study of cleavage): muscovite (mica),


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limonite, gypsum, calcite, galena.

Problem 4 (Study of fracture): quartz, jasper,

fibrous gypsum, asbestos.

Problem 5 (Study of colour in monochromatic

minerals): azurite, malachite, sulfur, graphite.

Problem 6 (Study of colour in alochromatic minerals): white, yellow, rose, green and smoked

quartz, green and violet fluorite.

Problem 7 (Study of streak): limonite, hematite,

cinnabar, magnetite, a piece of porcelain.

Problem 8 (Study of density): barite, quartz, cylinder, balance.

Problem 9 (Study of luster): galena, pyrite,

sphalerite, fibrous gypsum, quartz.

Problem 10 (Study of taste): silvine, halite, talc

and a cellulose paper to dry out.

Problem 11 (Study of birefringence): transparent calcite (Iceland spar).

Problem 12 (Study of mineral habits): gypsum in rosette habit, gypsum in bladed habit, aragonite

crystals, pyrolusite in dendritic habit, quartz in geode.

Problem 13 (Study of fluorescence): fluorite.


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PHYSICAL PROPERTIES OF MINERALS

Method: - Take a box and check the material inside.

- Read the information about your box and the

problem that’s to be solved. - Follow the instructions and solve the problem.

- Write down the information and solutions.

Draw a picture or take a photograph of each mineral in the box.

*Problem 1 (Study of hardness): Hardness is how

difficult is to scratch a mineral. This property depends on the union of the atoms involved.

a) Check which mineral scratches most easily .

Make a list from the softest to the hardest. b) Now scratch every mineral with the metal

screw. Which place on the list would you put the screw?

c) Take each mineral and try to scratch the glass. Which minerals can scratch the glass?


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To sum up: Which mineral is the softest? And

which is the hardest? Why?

*Problem 2(Study of magnetism): A mineral is magnetic if it is attracted by a magnet.

Find out if the minerals in the box are magnetic or not. Write down your answers.

*Problem 3 (Study of cleavage): Cleavage is the way a mineral breaks. Many minerals break along

flat planes, or cleavages—some in only one direction, other in two directions, and some in three

directions or more. In this case the minerals have already been broken.

Observe them and write down the name of those that have got cleavages.

*Problem 4 (Study of fracture): When a mineral breaks in irregular surfaces we speak about

fracture. If the mineral breaks with smooth flat surfaces we speak about cleavage. There are

different words to describe what a break in a rock

or mineral looks like: -conchoidal : curved break like what happens with

thick glass or bottle bottom, shell shaped, can be rough or smooth

-splintery : fibrous -uneven : rough surface, not smooth

In this case the minerals have already been broken. Observe them carefully and write down which of

them has fracture. Write down which kind of fracture they have.

*Problem 5 (Study of colour in monochromatic

minerals): There are minerals that always have the same

colour. They are called monochromatic.

All the minerals that you have in the box are monochromatic. Write down the colour of each

specimen.

*Problem 6 (Study of colour in alochromatic minerals): There are minerals that can have very

different colours, a variety of colours.


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All the minerals you have in the box are

alochromatic. Write down the colours of all the specimens. Which mineral of the box shows a major

variety of colours?

*Problem 7 (Study of streak): If you rub a mineral against a streak plate you will get a powder.The

colour of this powder is the authentical colour of the

mineral. Rub each mineral on the porcellain plate. Write

down the colour you observe. Is this colour different from the colour of the mineral?

*Problem 8 (Study of density): Remember that

density is the relationship between mass and volume: weight/volume.

To calculate density you have to fill a cylinder with water to a certain volume. You write down the

volume of water (V). Then, you add the specimen inside the cylinder and you write the new volume

(V´). The difference between both (V-V´) is the volume of the mineral. Weigh the mineral and write

down its mass.

Can you calculate the density of the mineral? What is the value?

*Problem 9 (Study of luster): Luster is the way a

mineral reflects light. We can describe it as metallic (very shinny) or non-metallic. There are different

words to describe non-metallic luster: dull/earthy, waxy (like the surface of a candle), greasy /oil,

pearly, silky (like a piece of cloth), glassy/vitreous (looks like a glass), resinous, adamantine (like a

diamond). Write down which kind of luster each specimen has.

*Problem 10 (Study of taste): Some minerals have

a characteristic taste and this property is useful in

identifying them. Water the top of three fingers and touch each

specimen with a different finger. Taste with the tip of your tongue every finger. Describe the flavour of

each mineral.

*Problem 11 (Study of birefringence): This property


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is very common in most of the minerals.

Tick a dot (*) on your sheet. Place the transparent calcite sample over the dot and look at it. What can

you observe? Explain what you think has happened.

*Problem 12 (Study of mineral habits): In some minerals there are typical associations of

crystals.

Match the following crystal habits to the correspondent mineral specimen:

a) bladed habit, b) rosette habit, c) dendritic habit, d) hexagonal habit e) geode

*Problem 13 (Study of fluorescence): We can check this property with an ultraviolet

lamp. Take a fluorite sample and place it under the uv lamp. Explain what happens.


Is COLOUR a good way TO IDENTIFY MINERALS?


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Some specimens of quartz, calcite, halite and feldspar are normally white. We need some other ways of telling them

apart. Using the property of hardness, try to distinguish calcite

from quartz: Rub an edge of the quartz on a surface of calcite .Rub an edge of the calcite on the quartz. What do

you see? Another test you can do: Calcite is a carbonate.

Carbonates produce carbon dioxide (gas) when a drop of hydrochloric acid is put onto the specimens. After putting

one small drop of acid, rinse off the acid. Another test is taste. Just touch the mineral with the tip

of your tongue. You can try these tests on all the four minerals and write

down what you find in the following table:

PART 2 ( rocks: granite, sandstone, some types of limestone)

One mineral of these minerals makes up a small part of

Quartz Calcite Halite Feldspar

Colour?

Shiny/dull?

Is it the hardest?

Is it the softest?

Has it a taste?

What does acid do?


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the granite. Most of the sandstone is this mineral. Is this

quartz, calcite or halite? Try your tests to INFER which one.

Granite also contains two kinds of feldspar. Feldspar is actually the most common mineral in the world. One

variety is white, what colour is the other? Investigate some types of limestone. Which of the four

minerals is in limestone?


Let’s make a geode of blue Copper Sulfate Crystals


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Geodes are a type of rock containing crystals. Normally,

millions of years are required for flowing water and minerals to deposit crystals. You can make your own

'geode' in only a few days. Grow beautiful translucent blue crystals of copper sulfate pentahydrate inside an egg

shell to make your own geode.

Material:

- an egg

- hot water

- copper sulfate

Method :

1. First, you need to prepare the eggshell. A natural

geode forms inside a mineral. For this project, the mineral is the calcium carbonate of an eggshell.

Carefully crack open an egg, discard the egg, and keep the shell. Clean the egg from the shell. Try for a

clean break, to create two halves of the shell, or you may wish to just remove the top of the shell, for a

more ball-shaped geode.

2. In a separate container, add copper sulfate to 1/4

cup of hot water. The amount of copper sulfate isn't exact. You want to stir copper sulfate into the water

until no more will dissolve. More is not better! It

should take a few pinches of solid material to make a saturated solution.


45

3. Pour the copper sulfate solution into the eggshell.

4. Place the eggshell in a location where it can remain undisturbed for 2-3 days. You may want to place the

eggshell in another container to keep it from falling over.

5. Observe your geode each day. Crystals should appear by the end of the first day and will be at their

best after the second or third day.

6. You can pour out the solution and allow your geode to dry after a couple of days or you can let the

solution fully evaporate (week or two).

Tips:

1. Even a small increase in the temperature of the water will greatly affect the amount of copper sulfate

(CuS04 . 5H20) that will dissolve.

2. Copper sulfate is harmful if swallowed and can

irritate skin and mucous membranes. In case of contact, rinse skin with water.

3. Copper sulfate pentahydrate crystals contain water, so if you want to store your finished geode, keep it in

a sealed container. Otherwise water will evaporate from the crystals, leaving them dull and powdery. The

gray or greenish powder is the anhydrous form of

copper sulfate.

4. The archaic name for copper (II) sulfate is blue

vitriol.

5. Copper sulfate is used in copper plating, blood tests

for anemia, in algicides and fungicides, in textile manufacturing, and as a dessicant.


Describing rocks


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We have heard of lots of kinds of rocks. Granite, sandstone, limestone and so on. How do we know which

one is which?

Part 1 You will be given a set of different types of “earth

materials”. Try to put them into groups of similar types. Write down why you put them together, and compare

your groups with those made by other groups. Do you agree?

Part 2

We need to find out how to describe what we see. The best way is to compare two types of rock.

Take two good-sized specimens of granite and sandstone.

Observe them carefully. How many differences can you find? The chart will help you.

GRANITE SANDSTONE____

- Colour?

- Size of bits?

- Shiny or dull?

- How many different types of bits?

- Anything else?


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LABORATORY PRACTICE 7 Identification of rocks

You are going to work as geologist teams. You will have

to identify the rocks after observing them carefully. You will have to say if they are sedimentary, igneous or

metamorphic and justify your decision. At the end of the class, each team will show the results to the rest of the

class and we will discuss the answers.

Each team will be given a collection of 6 rocks and an observation card. You will study each sample during 5

minutes. The observation card will help you to support

your decision.

Rock 1 It can be scratched with fingernail

It is lighter than the other rocks It has got a bright colour

We found it at the top of a mountain It makes your clothes dirty

It contains fossils

Rock 2 It is multi-coloured

It is heavier than the other rocks It is very hard

It contains crystals

It is difficult to break It reflects light

Rock 3

It is fragile, so it breaks easily It has got layers

It is almost black It is quite resistant

It can be used in roofs It is odourless


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Rock 4

It is not especially heavy It cannot be scratched with fingernail

It is dark We found it buried in a watercourse

It has not got crystals

Rock 5

The rock contain bits of other rocks It can break

It makes your clothes dirty It is easy to scratch

We found it on the base of a mountain

Rock 6 It is bright coloured

It is very hard It is difficult to scratch

It reflects the light We found it in a high altitude

We can use it as we find it in nature

OBSERVATION CARD:

Rock 1 We think this rock is ………. because ……….

Rock 2

Rock 3


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Rock 4

Rock 5

Rock 6


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Roser Canet_3r ESO_materials on the Earth Crust

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