Unit E Lesson E6 Properties of Rocks and Minerals
Completion requirements
Lesson E6: Properties of Rocks and Minerals
Video Lesson
Rocks are everywhere. Rocks are made of smaller parts called minerals. We use rocks and minerals for many things. How do we identify rocks and minerals, how do we tell rocks and minerals apart, and what do we use each for? Watch this video to learn more
about rocks and minerals.
Lesson E6: Properties of Rocks and Minerals
Rocks and Minerals and You
Rocks and minerals can be fun to spot when you are outside, and some people even collect their favourite finds. If your family has a farm, you might just consider rocks a serious nuisance. However, many people hunt actively for specific rocks and minerals, especially if they are rare or valuable. Gold, diamonds, and other gemstones (diamonds are a type of gemstone) are valuable minerals found in Alberta. For example, did you know that gold can be found in the North Saskatchewan, Red Deer, Peace, and Athabasca rivers?
Rocks and minerals can be fun to spot when you are outside, and some people even collect their favourite finds. If your family has a farm, you might just consider rocks a serious nuisance. However, many people hunt actively for specific rocks and minerals, especially if they are rare or valuable. Gold, diamonds, and other gemstones (diamonds are a type of gemstone) are valuable minerals found in Alberta. For example, did you know that gold can be found in the North Saskatchewan, Red Deer, Peace, and Athabasca rivers?
Reading for This Lesson
Science in Action 7
Materials:
Science in Action 7
Reading: Pages 369–376
Materials:
No other materials are required for this lesson.
Figure E.2.6.1 – Rocks are made up of many parts, including minerals.
Figure E.2.6.2 – Minerals are often bought and sold by collectors.
What are Rocks and Minerals?
Rocks are made of one or more types of material that have been stuck together. A close look at many rocks might show smaller pieces, or clumps, of the materials in the rock. These are called grains. Many types of rock have grains that reveal their contents or help explain how they have formed. For example, if the grains in the rock have formed perfectly from a single mineral, the grains may appear as crystals.
All rocks are made of one or more minerals. These minerals might be joined with some sort of natural cement to form a rock. Other rocks have minerals that are stuck together in other ways. Minerals are the building blocks of rocks.
Rocks such as granite and sandstone contain various minerals. Granite, for example, is feldspar, quartz, mica, and other minerals. Rocks such as marble and limestone are a single mineral, calcite. An upcoming lesson explores more about the relationship of limestone and marble.
Rocks are made of one or more types of material that have been stuck together. A close look at many rocks might show smaller pieces, or clumps, of the materials in the rock. These are called grains. Many types of rock have grains that reveal their contents or help explain how they have formed. For example, if the grains in the rock have formed perfectly from a single mineral, the grains may appear as crystals.
All rocks are made of one or more minerals. These minerals might be joined with some sort of natural cement to form a rock. Other rocks have minerals that are stuck together in other ways. Minerals are the building blocks of rocks.
Rocks such as granite and sandstone contain various minerals. Granite, for example, is feldspar, quartz, mica, and other minerals. Rocks such as marble and limestone are a single mineral, calcite. An upcoming lesson explores more about the relationship of limestone and marble.
Figure E.2.6.3 – Panning for gold.
Figure E.2.6.4 – You can see the grains (clumps of rock material) in this sample of granite. Granite is one of the most common rocks.
Figure E.2.6.5 – This is a sample of basalt. Basalt and granite are made of many of the same minerals, but look at how tiny the grains are in basalt. This gives us clues about how these rocks must have formed.
Properties of Minerals
Geologists have identified almost 5000 minerals on Earth. Every mineral is pure and different from every other mineral. Some minerals are very rare, and other minerals are very common. Almost every rock that we see is made of combinations of only five minerals; calcite, quartz, feldspar, mica, and hornblende.
Many minerals in rocks occur as crystals. An example of mineral crystals familiar to you is salt. If you have looked at salt under a magnifying glass, you have seen crystals of halite, which is sodium chloride, also known as table salt. Crystals form in various ways depending on the conditions and type of mineral.
Recognizing crystals of a mineral is one of the first steps to identify a mineral. This is why one of the most important tools for a geologist is a hand lens or small magnifying glass. A mineral’s crystals have a very distinct shape and often a recognizable colour.
Geologists have identified almost 5000 minerals on Earth. Every mineral is pure and different from every other mineral. Some minerals are very rare, and other minerals are very common. Almost every rock that we see is made of combinations of only five minerals; calcite, quartz, feldspar, mica, and hornblende.
Many minerals in rocks occur as crystals. An example of mineral crystals familiar to you is salt. If you have looked at salt under a magnifying glass, you have seen crystals of halite, which is sodium chloride, also known as table salt. Crystals form in various ways depending on the conditions and type of mineral.
Recognizing crystals of a mineral is one of the first steps to identify a mineral. This is why one of the most important tools for a geologist is a hand lens or small magnifying glass. A mineral’s crystals have a very distinct shape and often a recognizable colour.
Figure E.2.6.6 – Salt (NaCl, or halite) is a mineral that forms crystals, which are also known as grains.
What is a mineral? Watch this video in which a geologist explains details about minerals.
If the crystals of the mineral are visible, their colour and shape can be useful to help to identify the mineral. However, crystals are not always visible, and impurities in the mineral can produce many colours.
Often, other properties we can measure and observe must be used to confirm an unknown mineral. Consider the various properties of minerals that we use to identify them.
Often, other properties we can measure and observe must be used to confirm an unknown mineral. Consider the various properties of minerals that we use to identify them.
Colour
Lustre
Figure E.2.6.7 – The purple colour of the mineral amethyst is very distinctive. Amethyst is a gemstone.
Figure E.2.6.8 – Kaolinite is a mineral with a very dull, non-metallic lustre.
Colour is the easiest and quickest step in identifying a mineral, but it is not very accurate. Impurities mixed with the mineral can produce many colours. Various types of light can make minerals appear to have various colours. Often, other properties
that we can measure and observe must be used to confirm an unknown mineral.
The surface of every mineral reflects light in various ways. Two minerals that are the same colour can have very different lustres. Minerals that are metallic often shine, but non-metallic minerals appear dull. Other terms used to describe a
mineral’s lustre include waxy, pearly, silky, greasy, or brilliant.
Streak
Cleavage and Fracture
Figure E.2.6.9 – Hematite is a mineral that has an almost black colour, but its streak is always bright to dark red.
Figure E.2.6.10 – Selenite gypsum forms as crystals. It has cleavage that makes it take a distinct shape.
The streak is the trail of powder left behind when the mineral is dragged across a porcelain tile. The colour we see can be influenced by many factors, but a mineral’s streak is very consistent. Often, the colour of the streak is different than
the colour of the mineral.
Even if the crystals of a mineral are difficult to see, the way the larger pieces break apart can reveal the qualities of the crystals. Because the crystals of a mineral stack and form in a regular pattern (similar to building with Lego blocks), each
mineral breaks in a distinct way. If the mineral crumbles in a rough break, geologists say that it has fracture. If the mineral breaks into regular blocks or sheets, it is said to have cleavage. The way a mineral with cleavage breaks
apart is very consistent, and this helps to identify the type of mineral it is.
Hardness
Figure E.2.6.11 – Talc is considered to be the softest mineral. A diamond is 1600 times harder than talc!
Figure E.2.6.12 – Diamonds are minerals that are quite rare and very hard.
Every mineral has a distinct hardness. Some minerals are very soft, and you can gouge into them with a fingernail. Others are extremely hard and can cut glass. To measure a mineral’s hardness, we must use some sort of scale. A simple comparison
can be made using your fingernail (soft), copper wire (a little harder), an iron nail (harder), a piece of glass (even harder), and a kitchen tile (hardest of these materials). Geologists use the more accurate Moh’s hardness scale, which uses a series
of ten minerals to compare hardness. If one mineral scratches another mineral, it is harder than the first mineral. On Moh’s hardness scale, talc is the softness (Moh’s hardness of 1) and diamond is the hardest (Moh’s hardness of 10).
Geologists use other properties to identify minerals, too. The specific gravity of a mineral refers to how heavy it is. For example, gold has a high specific gravity, and it is very heavy. Another property is the reaction to being exposed to acid. Certain minerals, such as limestone and marble, fizz when acid is dripped onto them. Some minerals, such as magnetite, are magnetic. Other minerals, such as halite, taste salty. Minerals such as Afghanite glow under UV light.
Minerals such as limestone, magnetite, and halite are identified easily by choosing the correct property to test.
Figure E.2.6.13 – Minerals like Afghanite glow under UV light.
Connections
Connections: Mining
>> Panning for Gold
Gold in Alberta is usually found as “flour gold”. This is tiny specks of gold found mixed with black sand that contains other heavy minerals. These black sands are in specific places of some river systems because of the way the water flows through the twists and turns of the waterways it follows.
Because gold is very valuable, people search for gold as a hobby or as a source of income. Searching for gold in Alberta’s rivers usually involves panning and sluicing. These techniques are very useful because they rely on the fact that gold is heavier than many other minerals and it has a distinct colour and lustre. Gold’s properties include the following:
>> Panning for Gold
Gold in Alberta is usually found as “flour gold”. This is tiny specks of gold found mixed with black sand that contains other heavy minerals. These black sands are in specific places of some river systems because of the way the water flows through the twists and turns of the waterways it follows.
Because gold is very valuable, people search for gold as a hobby or as a source of income. Searching for gold in Alberta’s rivers usually involves panning and sluicing. These techniques are very useful because they rely on the fact that gold is heavier than many other minerals and it has a distinct colour and lustre. Gold’s properties include the following:
- Colour: gold yellow
- Lustre: metallic
- Streak: yellow
- Cleavage and Fracture: no cleavage
- Hardness: 2.5 to 3 on Moh’s hardness scale
Figure E.2.6.14 – Minerals like Afghanite glow under UV light.
Which of these properties do you think are the most important to finding gold when panning or sluicing in a river? And what exactly is sluicing? Watch the following videos to learn more about panning and to find what happened when a geology student from
NAIT in Edmonton tried to find gold by Athabasca sluicing.
Identifying Minerals
To identify minerals, geologists (and science students) perform series of tests to reveal the various properties of the unidentified sample. Often, the person testing has a special kit that contains a magnifying glass, a streak plate, and a Moh’s hardness scale.
To identify minerals, geologists (and science students) perform series of tests to reveal the various properties of the unidentified sample. Often, the person testing has a special kit that contains a magnifying glass, a streak plate, and a Moh’s hardness scale.
The following two websites allow you to look at various minerals and their characteristics:
The Virtual Rock Box: Minerals
The Virtual Rock Box: Minerals
Click each image to see the mineral’s name and some of its important properties.Virtual Mineral Identification Activity
Each sample has properties you can click to reveal. Can you identify any of the minerals before you see their names?
Figure E.2.6.15 – Minerals like Afghanite glow under UV light.
Watch as our geologist goes through the various steps in identifying a mineral.
Try It!
Virtual Lab: Identifying Minerals
Probably, you do not have a mineral identification kit nor do you have a source of easily identifiable minerals. Watch the following YouTube video. You will see the instructor testing five unknown minerals. Watch how each test is done, listen for the properties he gives, and complete the following table. Some of the spaces have been filled for you already.
Probably, you do not have a mineral identification kit nor do you have a source of easily identifiable minerals. Watch the following YouTube video. You will see the instructor testing five unknown minerals. Watch how each test is done, listen for the properties he gives, and complete the following table. Some of the spaces have been filled for you already.
Your unknown minerals are in this video.
Identifying Minerals Chart
DOWNLOAD this document. It has a chart that will allow you to complete the missing information as you watch the video clips.
You are given five unknown mineral samples to identify. You are told that the five minerals are pyrite, feldspar, calcite, galena, and quartz. (Click on each mineral name to see an example and to learn more about that mineral.)
| Property | Unknown #1 | Unknown #2 | Unknown #3 | Unknown #4 | Unknown #5 |
| YouTube time | 0:37 | 2:23 | 3:38 | 5:40 | 7:07 |
| Colour | dark gray | colourless | white - gray | ||
| Lustre | glassy | metallic | |||
| Streak | gray - black | ||||
| Cleavage or Fracture | cube / 3-planes | cube / 3-planes | pyramid / 4-planes | none / fracture | |
| Hardness | 3 | 6 to 7 | 6 | ||
| Weight (aka specific gravity) | heavy | light | medium | ||
| Mineral Name |
Questions:
Use this link to help identify each unknown mineral:
Hints:
Use this link to help identify each unknown mineral:
Hints:
- A “vitreous” lustre means almost the same as glassy.
- “Specific gravity” refers to how heavy the sample feels in your hand.
- Cleavage and fracture can be difficult to determine sometimes. Cleavage refers to the number of pairs of parallel sides the mineral has when it breaks.
Figure E.2.6.16 – “Rundle rock” is a popular building stone of limestone. Rundle rock was first mined near Mount Rundle, which is near Banff.
Figure E.2.6.17 – Saskatchewan is the world’s leading potash producer. This stockpile of potash has been removed from an underground mine.
Identifying Rocks
Because rocks are made of minerals, a very good way to examine an unknown rock is to identify the minerals. This is not always easy. In some cases, such as limestone, a single mineral test such as dripping weak acid and observing bubbles can indicate the type of rock. You will soon learn more about the specific classes of rocks, and you will test your powers of ‘rock-servation’.
Economic Importance of Minerals in Alberta
Minerals are very important in many ways. Minerals are added to our foods and personal care products, and they are used to build many types of structures.
Because rocks are made of minerals, a very good way to examine an unknown rock is to identify the minerals. This is not always easy. In some cases, such as limestone, a single mineral test such as dripping weak acid and observing bubbles can indicate the type of rock. You will soon learn more about the specific classes of rocks, and you will test your powers of ‘rock-servation’.
Economic Importance of Minerals in Alberta
Minerals are very important in many ways. Minerals are added to our foods and personal care products, and they are used to build many types of structures.
To name all the ways that minerals are used is difficult! Some minerals such as salt are fairly easy to obtain, but others are very difficult and expensive to prepare for use. In many parts of Canada, the mining of minerals is a very important part of
the economy.
Many minerals are mined throughout Canada, but potash and uranium mining are major industries in Saskatchewan. Potash is used as plant fertilizer. Uranium is a radioactive element used for production of electrical energy.
Alberta has many important minerals as well. Gold is a rare and valuable example, but Alberta has many more! Limestone, iron, salt, and magnetite mines are in various locations in the province, but Alberta has no underground mines. Currently, every mine in our province is a strip mine. This means the topsoil is removed (stripped) and trenches are dug to get at the materials. Materials buried deeper in the crust are obtained by using various drilling and pumping technologies.
Many minerals are mined throughout Canada, but potash and uranium mining are major industries in Saskatchewan. Potash is used as plant fertilizer. Uranium is a radioactive element used for production of electrical energy.
Alberta has many important minerals as well. Gold is a rare and valuable example, but Alberta has many more! Limestone, iron, salt, and magnetite mines are in various locations in the province, but Alberta has no underground mines. Currently, every mine in our province is a strip mine. This means the topsoil is removed (stripped) and trenches are dug to get at the materials. Materials buried deeper in the crust are obtained by using various drilling and pumping technologies.
Figure E.2.6.18 – Uranium mines similar to this are found in Northern Saskatchewan.
Panning for Gold
They say that money doesn’t grow on trees, but the next best thing can be found in the ground. Certain minerals are valuable, and for many years the only thing stopping you from claiming these minerals was a shovel and a map. In fact, this is exactly why there were several gold rushes throughout the world, including in Western Canada.
In the past there was a chance you could find gold in a stream, under a hill, or in a mountain cave. But If you had to know where to go, and you had to survive the journey to get there.
Find out more about searching for gold by clicking here to Explore with Elsie.
Make sure you have understood everything in this lesson. Use the Self-Check below, and the Self-Check & Lesson Review Tips to
guide your learning.
Unit E Lesson 6 Self-Check
Instructions
Complete the following 6 steps.
Don't skip steps – if you do them in order, you will confirm your
understanding of this lesson and create a study bank for the future.
- DOWNLOAD the self-check quiz by clicking here.
- ANSWER all the questions on the downloaded quiz in the spaces provided. Think carefully before typing your answers. Review this lesson if you need to. Save your quiz when you are done.
- COMPARE your answers with the suggested "Self-Check Quiz Answers" below. WAIT! You didn't skip step 2, did you? It's very important to carefully write out your own answers before checking the suggested answers.
-
REVISE your quiz answers if you need to. If you answered all the questions correctly, you can skip this step. Revise means to change, fix, and add extra notes if you need to. This quiz is NOT FOR MARKS, so it is perfectly OK to correct
any mistakes you made. This will make your self-check quiz an excellent study tool you can use later.
- SAVE your quiz to a folder on your computer, or to your Private Files. That way you will know where it is for later studying.
- CHECK with your teacher if you need to. If after completing all these steps you are still not sure about the questions or your answers, you should ask for more feedback from your teacher. To do this, post in the Course Questions Forum, or send your teacher an email. In either case, attach your completed quiz and ask; "Can you look at this quiz and give me some feedback please?" They will be happy to help you!
Self-Check Time!
|
|
Self-Check Quiz Answers
Click each of the suggested answers below, and carefully compare your answers to the suggested answers.
If you have not done the quiz yet – STOP – and go back to step 1 above. Do not look at the answers without first trying the questions.
Limestone is a rock mined in Alberta and made of just one mineral -- calcite.
The grains in a rock describe the general pattern of clumps that we see. If the grains have formed perfectly from pure minerals, they may appear as crystals.
A quick glance at a mineral reveals its colour. Minerals may be many colours, however, and impurities can change the colour of the mineral sample.
Pyrite looks like gold, and because gold is so valuable, many people people have been fooled when they have found pyrite.
A good way to test mineral hardness is to scratch them against each other. When two minerals of different hardness are rubbed together, the softer one will be scratched and the harder one will not. This can be repeated with all five minerals.
For example, if mineral “C” scratches mineral “A”, you know that “C” is harder than “A”. Continue the testing until all samples have been ranked.