Home made rocks
Earth Science - Rock properties; inquiry: observation,, evidence, classification, and reasoning to explain & understand (3rd - 4th grade)


This is an Earth science plan to investigate and explore rocks: their properties, different ways to classify them, and tests geologist use to study them. Make mystery rocks and use them to explore how a geologist uses different tests to discover rock properties and explain how they are formed and classified. (Sample rock pictures)

Home made rocks need to be made a week before they are used. Takes one week to set and dry.

Recipe - Makes about 18 rocks with a 5 cm diameter. Mix the flour, salt, and alum together



  1. Mix the water and add food coloring.
  2. Add the water to the flour mixture.
  3. Knead until it is uniform in color and texture and does not stick to the bowl. May add a little more water if the dough is crumbly.
  4. Add the sand and the gravel to the mixture and knead until it is well mixed.
  5. Divide the mixture into 18 equal pieces about the size of a ping-pong ball.
  6. Put a rock ball into the palm of your hand, and make a small hole in the center with your thumb.
  7. Place 10-23 oyster shell pieces in the hole and mold the dough around them.
  8. Work the ball of dough smoothing its surface and flatten it to about 2 cm thick.
  9. Put the rocks on top of paper towels in a tray so that they do not touch each other.
  10. Put them in a warm area to dry and turn them each day so they will dry thoroughly - about a week, depending on the humidity.
  11. NOTE: putting them in a microwave or oven will make them too hard
  12. DO NOT put any left over pieces of sand and gravel down a drain.
  13. May want to test one with a nail (the geologist's pick) after six days to see if it is dry inside. They should be dry enough to hold their shape and not crumble easily but soft enough to be broken in half and taken apart with the nail (the geologist's pick) without concern of a puncture wound with the nail. 

Recipe and activities source: FOSS (Full Option Science Systems)  from Britannica Encyclopedia Corporation.  Earth Science Module  

Background and preperation information to consider:

Depending on the experiences of the learners some or all of the following may need to be done before the first activity with the home made rocks.

Set the Stage. 

  Introduce rocks, observations, properties, measurement, and geologists

Introduce the Mock Rocks  

Concepts and outcomes

Content - Earth Science - Rocks and their properties

What we learn with science - enduring understanding, big ideas, generalizations)

Rocks are composed of Earth materials.

Related concepts and facts -

  • Rocks are composed of earth materials - sand, silt, humus (leaves, plant parts, animal parts, microorganism), gravel, rocks ...
  • Rock properties include luster, hardness, color, mass, density, crystals and if present their size,

Outcome - Rock properties

Describe properties of rocks.

Specific outcomes -

  1. Identify common properties of rocks (color, hardness, crystals, grainy, size, luster).
  2. Describe rocks by their properties.
  3. Identify rocks by common properties.


Inquiry Processes

Observation and properties

How science explores and uses observation and properties to understand and explain.

Properties can be used to identify and describe objects.

Related concepts and facts -

  • Observation can be used to identify properties of objects.
  • Objects have many properties.
  • Objects can be described and compared by properties.
  • Properties are size, color, shape, texture,


Make observations, identify properties/ characteristics and use them to describe objects.

Specific outcomes -

  1. Describe an object by its properties.
  2. Describe the term - property and provide at least two examples (color, hardness, texture, luster, crystal, mass, size, shape, temperature, amount, volume, rate, ...
  3. Recognize that some properties are necessary to include when describing an object.
  4. Recognize that a sufficient number of properties needs to be included to describe an object.
  5. Recognize a unique set or properties is required to distinguish a unique object.


Systems, order, organization, & classification

How science uses properties to organize objects as similar or different and make groups with similar properties (classification).

Related concepts and facts

  • Properties/ characteristics can be used to group objects.
  • Objects can be grouped by similar properties/ characteristics.
  • Classification systems can be changed by changing the properties/ characteristics used to group the objects.


Group and regroup rocks based on observed properties.

Specific outcomes

  1. Classify objects by their similar properties or characteristics.
  2. Create a classification system to classify rocks.
  3. Modify their classification system to include additional properties
  4. Use their classification system to classify unfamiliar objects (rocks).
  5. Group and regroup rocks based on observed properties.
  6. Students will suggest a classification system, that operates like the one created and used for rocks, could be created and used to classify animals or plants or other things with many properties.


Pedagogical ideas

Activity sequence

  1. Observe home made rocks
  2. Draw and record observations with explanations as to similarities and differences.
  3. Taking apart the home made rock activity.
  4. Separate home made rock powders with water.
  5. Discuss how different properties: such as luster, & hardness. Measure them: can it be sanded? Paper clip scratch test.
  6. Test for calcite
  7. Granite
  8. Moon rocks, other planets ...

Related plans with activities


Focus questions




Exploration procedure for home made rock

  1. Show learners a home made rock.
  2. Ask. How can you learn about these rocks?
  3. Tell them they are going to investigate them. 
  4. Assign groups of four.
  5. First, observe them and describe their properties in their lab notes.
  6. If necessary, discuss how to record.  The first observations they are going to make is the surface of the whole rock. They should make a sketch of their rock in their lab notes Challenge them to find out as much as they can about what makes up the rock by observing its surfaces and noting them in their notes.  
  7. Make Measurements.  Review measurement language the tools they will use make their measurements.  Diameter is the distance across an object. Circumference is the distance around the object. Depth is the distance through the object. Weight is how much the object weighs.  
  8. Make Magnified Observations.  Introduce the hand lens as another tool that geologists use to get a closer look at rocks.  Show the students the appropriate technique for using the hand lens.  Tell them to choose an interesting section of their rock to look at through the lens.  Ask them to draw a picture of this view through the hand lens in their notes.  Show how to mark the part of the rock they view through the lens on their larger drawing.  
  9. Divide into pairs.  Explain each group of four should divide into two teams.  One getter for each group of four will bring all of the equipment the two teams will share.  
  10. Instruct the getters to pick up four paper plates, two rocks for their group.  Then come back for the measuring tools and hand lenses as the teams need them.  Each group needs one balance, one set of weights, two plastic cups and one meter tape.  Each team should return the measuring tools when they finish making and recording their measurements.
  11. Compare observations and list the properties of the rocks discovered. 
  12. Tell. A reader for each team to report the diameter of their rock.  Find out which rock had the smallest diameter.  Repeat the procedure the other rock measurements so the learners can experience reporting data.
  13. Ask them to describe what they saw through the hand lens. 
  14. Review, they have been looking at the properties of the rocks (color, texture, size, shape, etc.).  
  15. Discuss how the students would find out more about their rocks. 
  16. Explain geologists use tools such as picks to carefully take apart rocks to observe of what rocks are made.  Show them the nail, their geologist's pick.  
  17.  Explain their next challenge is to identify as many different parts of the rocks, or rock ingredients, as they can.  Tell them.
    • Each person will work with half a rock and carefully separate out the different ingredients.
    • Count or estimate how many of each kind of ingredient they find.
    • Combine your count of ingredients with your teammate's findings so you have the total ingredients in one rock.
    • Record the result in their notes.
  18. Break the rocks in half and help the teams break their mock rocks in half as necessary and start their investigation.  If the rocks are too hard to break apart by hand, help them carefully use the nail to chip the rock in half. Have the getters get four nails, one for each person. 
  19. Pairs work with their rock on a paper plates, separate the different ingredients, and into separate piles on their plates.
  20. When the rocks have been separated into the different materials and data recorded, ask them to share their findings.
  21. Make a list on the board of ingredients they found (two colors of gravel, shells, sand). 
  22. Ask. How  much of each ingredient they found?
  23. Explain. Real rocks are Earth materials made up of more than one ingredient which can be separated into their different parts, although it isn't as easy as taking a mock rock apart.  
  24. Look at the leftovers.  
  25. Tell them to describe this material, and ask.
  26. How do theu think they could separate this rock material further?  
  27. After the students respond, tell them that they will have a chance to take apart the remaining rock, but first they need to collect the gravel.  
  28. Collect the Gravel and Shells.  Provide two cups for each group.  Have each group put all their gravel in one cup and the shells in the other.  Have the getters bring the cups to the materials station. 
  29. The students will have unseparated rock material remaining on the plates, but it shouldn't contain much gravel or many shells.  

If the activity needs to be divided into two sessions, this is a good place to store materials and transition for another day.

  1. Introduce the vials. 
  2. Tell the class that each pair of students will get a vial and a lid.  They should fill the vial one-third full of the remaining rock material, create a label with their names, put the label inside the vial, and put the lid on.  Any extra material not placed in the vial can be thrown away.  The plates can be brushed off and saved.
  3. Tell the students where to store their labeled vials of unseparated materials, wash hands and clean up their desk tops.  
  4. Can review and close the lesson.
    • Ask. What are some of the properties of the home made rock?  (recall)
    • How did you separate the ingredients?  (recall)
    • What tools would you need to take apart a real rock?  (integrating)
    • How were the rocks you took apart like real rocks. 
    • How were they different?  (open-ended)  
    • Vocabulary review: earth material:  a substance that makes up or comes form the earth. geologist:  a person who studies the earth and the materials of which it is made. property:  a characteristic of an object; something you can observe such as size, color, shape, or texture. rock:  an earth material composed of different ingredients, a mixture of ingredients Size descriptors circumference:  the distance around an object. depth:  how thick an object is from top to bottom. diameter:  the distance across a round object.        

Next activity Rocks in water

  1. Ask. How might the left over fine material in the vials be separated further?
  2. Have each group take a vial with the powder in it and add 25 ml of water. Put the lid on the vial, hold tightly, and shake.
  3. Observe and draw the contents.
  4. Let it rest over night and draw the settled contents.
  5. Slowly and gently pour the liquid from the vial into a flat evaporating dish or plate to barely cover the bottom.
  6. The settled material can be discarded and the vial cleaned.
  7. Observe until the liquid is gone. If a fan is available, might ask students how the process could be sped up. Then gently blow air over the area.
  8. Draw their finding and share results (Small square crystals with X's in them.) When water was added, the salt was dissolved in the water. When the liquid from the vial was poured into the evaporating dish, the dissolved salt was left after the water evaporated.


The home made rock was made from: gravel, sand, shells, flour, water, food coloring, alum, and salt. The flour and alum need not be specifically identified other than powder.

Activity Scratch test

Use a paper clip for a scratch test.

  1. Depending on the rocks you can find, select four, preferably the hardest quartz which will not be scratched by the paper clip.
  2. Demonstrate the paper clip scratch test on a piece of chalk.
  3. Try the scratch test on four different rocks and order them by their hardness (calcite, quartz, gypsum, and fluorite) Use the paperclip, penny, and their finger nail).
  4. Record data on the chart - for each tool write yes or no if it scratches the mineral. Write a summary of the results in the last column. Add other rocks to the table of Mohs hardness.

Mohs hardness

1 - talc

2 - gypsum

3 - calcite

4 - fluorite

5 - apatite

6 - orthoclase

7 - quartz

8 - topaz

9 - corundum

10 - diamond

Minerals are ingredients of which rocks are made. There are over 2 000 of them.

Activity Calcite quest

Calcite quest - calcite is the only mineral that makes bubbles with acid (vinegar). Take four rocks, put them in 25 ml of vinegar, let it stand 24 hours, and compare the results with a control of 25 ml of vinegar. The rock samples can be rinsed and reused several times.

Rocks to test - granite, limestone, marble, sandstone. Record which create bubbles.

Review properties of calcite - hardness, bubble, color...

Do the vinegar test on calcite, remove liquid and evaporate it.

Next day observe rocks are done fizzing and liquid...

Pour liquid into an evaporation dish and set aside to observe later. Remember to include the control (vial with only vinegar). Compare the vinegar only to the calcite (crystals) and the residue in the dishes for the other rocks.

Oher rocks to test: Portland cement, limestone, seashells, ...

Activity more rocks

Minerals to investigate - mica, feldspar, quartz, hornblende, calcite, granite,


Assessment ideas

  1. What is a rock? A rock is an earth material composed of one or more minerals. Rocks we have studied include granite, limestone, marble, and sand stone. recall
  2. Name some rocks we have studied. varies by rocks available.
  3. What is a mineral? A mineral is a basic earth material, an ingredient in a rock that cannot be physically taken apart any further. Minerals we have studied include calcite, feldspar, fluorite, gypsum, hornblende, mica, and quartz. recall
  4. Name two minerals.
  5. How can you tell mica and hornblende apart? Both are black, but mica has a special property. It pulls apart in paper-thin, flexible sheets. The hornblende looks more needle- like and fibrous. recall
  6. What were the minerals you found in granite? Mica, feldspar, quartz, and hornblenderecall
  7. If you found a new rock, how would you find out what minerals are in it? Any and all of the tests studied in the module: scratch test, acid test, looking
    for specific properties
    integrating comrehension synthesis
  8. Why do you think people use granite to construct bridges, buildings, and monuments?
  9. What do you think is the most interesting property of a rock or mineral we have investigated?
  10. How do you think minerals get mixed together to make rocks? thematic connection: Interaction, Change
  11. If an author wrote that a rock is like a chocolate chip cookie, what do you think the author had in mind?
  12. What would be a good use of a very hard mineral like quartz?
  13. How would you find out the hardness of three minerals if you didn't have any tool with which to scratch them?
  14. Suppose you found a brick near your school. How could you find out if calcite is an ingredient in the brick?


Lab Notes

Home made rocks

Rock drawing






Table of materials found in the home made rock and its properties. Draw a picture of each rock material that is found in the first column, in the second describe its properties, and put additional notes in the third.

Rock materialsPropertiesNotes




















Rocks in water

Draw the vial before and after settling.




Draw what was in the evaporating dish.




Hardness chart


Mineral Paper clip Penny Finger nail Tools that scratched this mineral
1. calcite        
2. quartz        
3. gypsum        
4. fluorite        


Picture of rock




Possible kind of rock




fingernail _____ penny ______ paper clip _____ nothing _____


shiny ______ not shiny _____


Mohs hardness


Mohs hardness

1 - talc

2 - gypsum

3 - calcite

4 - fluorite

5 - apatite

6 - orthoclase

7 - quartz

8 - topaz

9 - corundum

10 - diamond


Dr. Robert Sweetland's notes
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