Home made rocks
Earth Science - Rock properties; Inquiry Process - Classification, observation, evidence, and reasoning to understand (3rd - 4th Grade)



This investigation explores rocks, their properties, and different ways to classify rocks. (Sample rock pictures)

Special materials - home made rocks need to be made a week before their 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

250 ml (1 cup) white flour
125 ml (1/2 cup) salt
10 ml (2 tsp) alum
125 ml (1/2 cup) water
5 drops red food coloring
5 drops blue food coloring
3 drops yellow food coloring
250 ml (1 cup) coarse sand
125 ml (1/2 cup) gravel - 2 different colors
30 ml (1/8 cup) oyster shell pieces


  1. Mix the water and add food coloring
  2. Add the water to the flour mixture. 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.
  3. Add the sand and the gravel to the mixture and knead until it is well mixed.
  4. Divide the mixture into 18 equal pieces about the size of a ping-pong ball.
  5. Put a rock ball into the palm of your hand, and make a small hole in the center with your thumb. Place 10-23 oyster shell pieces in the hole and mold the dough around them.
  6. Work the ball of dough smoothing its surface and flatten it to about 2 cm thick.
  7. Put the rocks on a top of paper towels in a tray so that they do not touch each other.
  8. 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. NOTE: putting them in a microwave or oven will make them too hard
  9. DO NOT put any left over pieces of sand and gravel down the drain.
  10. May want to test one with a nail (the geologist's pick) after six days to see if it is dry inside.


Earth Science - Rocks and their properties

(What science says - 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 inquires - process, skill, methodolgy)

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.


Inquiry Processes - System, order, organization - classification

Properties can be used to organize objects as similar or different and into 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.

Outcome - Inquiry Processes - System, order, organization - classification

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.



Activities to provide sufficient opportunities for students to attain the targeted outcomes.

Possible 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 the different properties such as luster, hardness, can it be sanded? and paper clip scratch test.
  6. Test for calcite
  7. Granite
  8. Moon rocks, other planets...

Pedagogical ideas

Focus questions - What is a rock? What are the properties of rocks? From what are they made? How are they made?


Activity 1-4

Materials:  Home made rocks, pick (nail) magnifying glass, paper plate, small vials to put separate parts of the home made rock in, lab notes


Instructional procedure

  1. Show students a home made rock and ask how they could find out about their rocks.
  2. Explain that geologists use special tools such as picks to take apart rocks and today they will use a nail as a pick.
  3. Challenge them to identify as many different parts of the rock, or rock ingredients.
  4. Pairs can work with a rock on a paper plate and separate the different ingredients and put them into different containers.
  5. Ask how the left over fine material might be separated further.
  6. 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.
  7. Observe the and draw the contents. Let it rest over night and draw the settled contents.
  8. Slowly and gently pour the liquid from the vial into flat evaporating dish or plate to barely cover the bottom.
  9. The settled material can be discarded and the vial cleaned.
  10. 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.
  11. 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.

Summary - 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 5

Using a paper clip for a scratch test. Depending on the rocks that you can find select four preferably the hardest quartz which will not be scratched by the paper clip.

Demonstrate how the paper clip scratch test on a piece of chalk.

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).

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.

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 6

Calcite quest - calcite is the only mineral that makes bubbles with acid (vinegar). So they will 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 also.

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 vial that had only vinegar. Compare the vinegar only to the calcite (crystals) and the residue in the dishes for the other rocks.

Portland cement, limestone, seashells...

Activity 7

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

Create a lab sheet for each rock sample to record properties for each. Name, color, hardness, luster, other...

Challenge students to find the minerals in a piece of granite. (hornblende, feldspar, quartz, mica) (there will be no calcite, but they should do the test to see)


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.

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 hornblende] (recall)

7. If you found a new rock, how would you find out what minerals were in it?

[Any and all of the tests studied in the module: scratch test, acid test, looking
for specific properties] (integrating)

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 gated?


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

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 materials Properties Notes



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 _____


Dr. Robert Sweetland's Notes ©