Rocks really rock! A lesson on the classification of rocks

This lesson will help students classify various rocks according to specified criteria. It will also help students classify a given rock using selected mineral identification tests. Students will use a graphic organizer to display their findings.

A lesson plan for grade 4 English Language Arts and Science

By Grace Smith

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Related topics

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Learning outcomes

Students will use several hands-on activities to analyze and classify various rocks. They will collect several different rocks and test each one for hardness, streak, and for the presence of carbonate.

Teacher planning

Time required for lesson

75 minutes

Materials/resources

• selected rocks: talc, granite, marble, agate, etc.
• pencil and paper
• penny
• paper clip
• small paper cups
• piece of glass or mirror
• chalk
• vinegar
• paper or plastic bag
• access to a concrete sidewalk
• eyedropper
• masking tape

Pre-activities

Students will participate in a rock scavenger hunt on the school grounds. They will hunt for a large rock, a small rock, a pretty rock, an unusual rock, and a rock with two or more colors. They will place their rocks in a paper or plastic bag as they collect them.

Activities

1. When students have returned to the classroom, they will label each of their rocks #1–#5 using the masking tape.
2. Working either individually or in pairs, students will perform the following tests:
   • Students will attempt to scratch each of their rocks using a fingernail, a penny, and a straightened paper clip. Also, they will attempt to scratch the glass with each rock. They will indicate their results on the matrix using yes or no.
   • Students will stroke each of their rocks across a concrete sidewalk in an attempt to see their rocks’ streak. Streak is the color of a mineral’s powder. Rocks will streak only if stroked across a surface harder than itself.
   • To test for the presence of carbonate, distribute a piece of chalk and a small cup of vinegar to each student. Using an eye dropper, the student will drip a small amount of vinegar on the chalk and observe the results (a small amount of fizz). The student will repeat the procedure on each of his/her rocks and record the results on the matrix.

Assessment

• Students will determine which of their rocks is hard (it scratches glass) and which is soft (it can be scratched by a fingernail, a penny, or a paper clip) by using the recorded results on the matrix.
• Students will classify their rocks according to whether or not the rocks leave a streak.
• Students will classify their rocks according to the presence or absence of carbonate using their recorded results on the matrix.

Supplemental information

Teachers should be familiar with Friedrich Mohs’ hardness scale.

Comments

My students really enjoy collecting and classifying rocks. Their interest remains high for quite some time as they share rocks with each other. If possible, invite a member of the local rock and mineral club to visit the class. Sometimes, we use aquarium gravel in various colors to make pebble mosaics as a follow-up activity.