Can you tell the difference?

Find the differences between the following two images.

To complete the spot the differences puzzle you previously explored, sight was the dominant sense used. There are other senses like smell and touch that can be used when examining things like rocks and minerals.

When geologists examine rocks and minerals, they use all of their senses and more.

My pet rock

Find a rock that will easily fit in your hand. Pick one up from your local environment or playground. Get to know your rock by examining it carefully. Use all your senses except for taste. Draw a picture of your pet rock. If possible, add texture and color to your drawing.

If you cannot find a rock of your own, you can draw a pet rock, or you can imagine the following rock is your pet rock:

Classification of rocks

This learning activity highlights people, places, or innovations that relate directly to the province of Ontario. Enjoy the exploration!

Geologists classify rocks into three groups. These groups are based on how the rock was formed in nature. The three groups are:

• sedimentary
• igneous
• metamorphic

Sedimentary rock

Sedimentary rock is formed at the surface of the Earth. It could be formed in water or on land. This rock is formed from eroded bits of rock, minerals, sand, and animal or plant materials that are deposited by water, wind, or ice, and then packed together in layers over a long period of time. This type of rock is fragile and can crumble and erode easily. Does your pet rock have layers?

Some examples of sedimentary rock include:

• sandstone
• shale
• siltstone

Fossils

Fossils form while sedimentary rocks are formed. Layers of the silt and sediments build up on the remains or traces of plants and animals that lived long ago. Over time, the layers turn into hard rock. The fossil stays preserved in its shape by the hard rock around it. Fossils give scientists clues about the past and help them to study the plants and animals that lived long ago. For example, the fossil from the previous image is a trilobite. The trilobite lived in Ontario between 520 million years ago (mya) to 251 mya.

Are there any fossils in your pet rock?

Check out the following video about fossils and what they can tell us about the history of our world!

Igneous rock

Igneous rock is formed when molten rock from below the Earth’s surface rises towards the surface, cools, and solidifies. A volcano is an example of magma coming to the surface. Crystals form on the rock as it cools. The surface of the rock and the crystals that form will be different depending on how fast the rock cooled.

Does your pet rock have shiny crystals?

Some examples of igneous rock include:

• granite
• basalt

Metamorphic rock

Metamorphic rock starts as sedimentary or igneous rock, and changes into metamorphic rock as a result of a large amount of heat or pressure acting on it over a long period of time.

Does your rock sound like it’s metamorphic?

Some examples of metamorphic rock include:

• marble
• slate

Check your understanding

Use your knowledge of the three classifications of rock to answer the following fill-in-the-blank questions:

For each sentence, select the missing word from the drop-down menu.

Examining a rock

Before beginning your experimentation, explore the following video that explains the scientific experimentation process. This will help guide you as you work your way through this activity.

Check out the following video to learn about the steps of the Scientific Experimentation Process.

Geologists use specific tests and criteria to classify rocks.

Magnetism

Geologists have found that some rocks contain minerals that make the rock magnetic. Magnetite is a mineral commonly found in igneous rocks that makes a rock react to magnets. Not all rocks are magnetic.

If you have a rock, check it for magnetism with a magnet, if possible.

Mineral scratch test

Geologists use the mineral scratch test to determine the hardness of a rock or mineral.

If you have your own rock, try scratching your pet rock with your fingernail.

If a fingernail leaves a scratch, then this indicates a hardness of 2 or less on the Mohs Scale of hardness. The rock may contain talc, a soft mineral.

If copper can scratch the rock, this indicates a hardness of 3 or less on the Mohs Scale. The rock may contain alabaster. If you have an old penny available, try scratching the rock.

If a steel file or nail file can scratch the rock, this indicates a hardness of 7 or less. The rock could contain quartz, for example.

Mineral streak test

Geologists sometimes perform a mineral streak test on rocks to find out what kinds of minerals are in the rock. A mineral’s streak is the color it has when it is ground to a powder.

Streak tests are performed using porcelain plates. If one is unavailable, an old kitchen or bathroom tile, or even a sidewalk can be used.

Check out the following video entitled “Streak Test for Minerals” to learn more about how to perform a mineral streak test.

If possible, perform the streak test on your pet rock.

Lustre

Geologists will also examine rocks under a light. They are looking to see if the rock is shiny. This shininess is called lustre.

Using a light, examine the surface of your rock. Does the rock look dull, metallic, shiny, glassy, or oily? Rocks are a combination of minerals and other materials like sand and organic materials. Not all rocks will have lustre.

How about your pet rock? Any shiny bits?

So, what’s the big deal about rocks and minerals?

Now that we know a bit more about rocks and minerals, think about where you’ve seen rocks and or minerals. Try to come up with at least 5 ways. You may wish to record your answers on paper, digitally, or orally.

Did your list include:

• gravel roadways
• river or road embankments
• sitting areas at a local park or school
• part of landscaping
• maybe jewelry?

Rocks and minerals are a very important part of our daily lives. We use stone, sand, and gravel for concrete, a building material for roads, buildings, and airports. Aluminum is used for drink holders and a variety of sizes of cans, window frames, and even airplane parts. Without salt, some people would find our foods rather tasteless and, in the winter, our roadways, unsafe. Cobalt has become a very valuable and important mineral, as our cell phones, laptop computers, and tablets all use lithium-ion batteries, for which cobalt is the raw material.

Though we depend upon rocks in minerals in so many ways, there is an environmental cost. Open pit and shaft mining may pollute air and drinking water, and affect wildlife and their habitats. The road salt we use in the winter may end up in our waterways, damaging those sensitive ecosystems. Recycling may seem like the answer, but sometimes it’s expensive or really difficult to do. We need to be careful about these resources.

Comparing rocks (testing rocks)

Geologists perform tests on rocks to determine what type of rock it is and what minerals the rocks may contain. This is especially important when mining companies are looking for a particular mineral to mine. Ontario has some of the world’s top mines. Gold, platinum, nickel, and copper are just some of the minerals being mined today.

Geologists will perform some of the tests you have learned in the Action part of this lesson on rocks they have found to determine if they contain valuable minerals like gold or copper.

Is it a rock?

Reflection

As you read through these descriptions, which sentence best describes how you are feeling about your understanding of this learning activity? Press the button that is beside this sentence.

Now, record your ideas using a voice recorder, speech-to-text, or writing tool.

Press ‘Discover More’ to extend your skills.

Discover More