Bring a Rock

By Elizabeth Watt


This activity is designed as a pre-lab to be done as an introduction into the study of rocks and minerals. Each student will collect a rock and describe it in detail in writing. The rock and the description will be brought to the classroom. All of the rocks will then be put into one group and mixed up, This large group of rocks will then be divided randomly into groups; one group for each lab group(2-3 students) in the class. As a team, each lab group will divide their group of rocks into subgroups based on any type of classification that the team agrees on. This classification system should be written down.

Teacher Background Information

All rocks are classified into one of three major groups; igneous, sedimentary and metamorphic. Before you begin a discussion of the differences of these rock types, this activity will give the students a chance to comp re rocks and describe any similarities or differences that they can observer This will also give the students a chance to experience some of the same difficulties that scientists encounter when attempting to classify rock samples.

Student Background Information

When you are asked to classify a group of objects, you are being asked to divide the group of objects into smaller groups based on characteristics or properties. All of the objects that you put together into one of the smaller groups should have at least one similar characteristic. In this activity there are no wrong answers. As a team, however, you must agree on the classification system you are using and each member of the team should be able to describe the system in writing and orally to me or to another team.


  • one rock
  • one 3 x 5 index card with a description of: where the rock was collected unique characteristics
  • pencil
  • paper
  • group of at least 10 rocks


Observe and describe rock characteristic Classify a group of rocks into subgroups.


(before lab day)

  1. 1. Collect/choose a rock.
    2. Using a 3 x 5 index card, write a description of your rock.  This description should allow you to identify this rock after it has mixed in with all of the rocks brought in by all of the other students in all of the other earth science classes.
    3. Hand in your rock and your index card by the due date.

(lab day)

  1. Lay all of your rocks from your bag onto the table
  2. Divide the rocks into smaller groups based on characteristics that the rocks have in common.
  3. Write a description of the common characteristics for each group.

Teaching notes

As the lab groups are working, walk from group to group listening to the discussions.  At least once during the activity, each lab group should orally give you the characteristics they have observed. As a lab group finishes and is waiting for the other groups, ask them to discuss the different ways the rocks might have been formed.
When all the lab groups have finished writing the description for each subgroup, one person from each group should give a brief report of their results.  As you continue this process around the room, you nd the students should be listening carefully for similarities and differences of terms used by each group.

Activity Extension

After the completion of the unit on rocks and minerals you may want to bring out the bag of rocks again.  It might best if each lab group had the same bag of rocks as the first time.  It also might be beneficial if the written description of their classification system could be returned to each group, Now that the students have some knowledge of common minerals and rock formation processes, ask them to group the rocks again and note any differences in the present classification and the previous system.