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.
UNIT 1 – MATERIALS ON THE EARTH
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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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- 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.
UNIT 1 – MATERIALS ON THE EARTH
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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);
UNIT 1 – MATERIALS ON THE EARTH
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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
UNIT 1 – MATERIALS ON THE EARTH
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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
UNIT 1 – MATERIALS ON THE EARTH
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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.
UNIT 1 – MATERIALS ON THE EARTH
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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),
UNIT 1 – MATERIALS ON THE EARTH
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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.
UNIT 1 – MATERIALS ON THE EARTH
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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?
UNIT 1 – MATERIALS ON THE EARTH
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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.
UNIT 1 – MATERIALS ON THE EARTH
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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
UNIT 1 – MATERIALS ON THE EARTH
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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.
LABORATORY PRACTICE 3
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?
UNIT 1 – MATERIALS ON THE EARTH
43
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?
LABORATORY PRACTICE 4
Let’s make a geode of blue Copper Sulfate Crystals
UNIT 1 – MATERIALS ON THE EARTH
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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.
UNIT 1 – MATERIALS ON THE EARTH
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.
LABORATORY PRACTICE 5
Describing rocks
UNIT 1 – MATERIALS ON THE EARTH
46
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?
UNIT 1 – MATERIALS ON THE EARTH
47
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
UNIT 1 – MATERIALS ON THE EARTH
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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
UNIT 1 – MATERIALS ON THE EARTH
50
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