Rocks, Rocks, Rocks: Test, Identify Properties & Classify

Learning Objectives

After this activity, students should be able to:

• Gather data by performing scientific observation and testing of rocks.
• Use the data and a flowchart to determine rock types and rock classification.
• Identify rock types by distinguishing features.
• Relate rocks-in-hand to geological formations on maps.
• Relate the relevance of each tested/observed rock characteristic to designing/building caverns.

Materials List

Each group needs:

• rock testing kit (see component list, below); such as the Home Science Tools 15-specimen rock test kit (containing the necessary 8 rock samples)
• (optional) mineral testing kit, such as the Home Science Tools mineral test kit
• textbook or reference to classify the rocks (igneous, sedimentary, metamorphic)
• paper towel
• 3 handouts: Rocks, Rocks, Rocks Worksheet; Rock Test Data Table; Rock Identification Flow Chart

Each rock testing kit needs:

• 8 rock samples of the rocks listed on the Alabraska Geology Map: basalt, sandstone, limestone, granite, gneiss, slate, pumice, obsidian (not sand/gravel)
• steel nail
• copper penny
• streak plate, such as an unglazed porcelain tile
• magnet
• hydrochloric acid; alternatively, use vinegar
• magnifying glass
• small piece of glass
• small steel plate
• piece of quartz
• cup of water

Introduction/Motivation

Some rocks are not suitable for caverns. So, to determine the best place to locate your cavern, you need to get an understanding of the types of rocks and their properties throughout the varied terrain of the state of Alabraska.

Different rock types vary by region, so today you will be performing some rock tests so you can learn their properties, identify them and classify them as sedimentary, igneous or metamorphic.

• Igneous rocks are formed directly from the cooling of magma and make up the majority of the Earth's crust.
• Sedimentary rocks are often called "secondary" rocks, because they form from small pieces of other types of rocks, or from minerals that were previously dissolved in water (like the silt in lakes, rivers and seas). These are commonly found in dry areas.
• Metamorphic rocks are those that have been changed over time due to different chemical surroundings, heat and pressure.

Pre-Req Knowledge

A general familiarity with rocks and minerals.

Procedure

Background Information

As necessary, supplement students' understanding of basic rock/mineral testing, rock identification, and rock classification (sedimentary, igneous, metamorphic).

The basic explanation of the rock cycle follows: Rocks are pushed deep into the Earth's surface, usually by tectonic motion, where they melt into magma. At a volcano, or anywhere magma is exposed to become lava (such as at divergent tectonic plates), the magma/lava cools to become igneous rock. Several processes may occur after this, for example kaolinization, which generates granite and other common igneous rocks. Metamorphic rocks are created in a different process than igneous rocks, a process that is characterized by high temperatures and pressures, changing the physical and chemical properties. These high temperatures and pressures are found in mountain-building events or through close proximity to igneous intrusions, where high temperatures exist from the cooling magma. Rocks exposed to the atmosphere suffer weathering and erosion, breaking into smaller fragments. The fragments accumulate, compress, and fuse to generate sedimentary rocks, such as limestone.

Before the Activity

Gather materials and make copies of the handouts.

With the Students

1. Start with a class discussion about rock properties and rock classification:

• Describe the various rock characteristics: luster (how light is reflected), hardness (ability to resist being scratched), granular (texture of the specimen), porous (how many small holes/pores), color.
• Describe the various rock names (refer to the Alabraska Geology Map) and the three rock classifications: sedimentary, igneous and metamorphic.
• Illustrate the rock cycle and emphasize the different formation routes of the three main rock types. The following diagram is useful.

2. Distribute rock testing kits and handouts to each team. Three possible ways to distribute the rocks and conduct testing:

• Quickest and most suitable for a mature class: Give each team all the rocks to test and discuss the results as a class after all testing and identification has been performed and recorded. 
• Give each group a different rock and after 5 minutes of testing, stop the class. Discuss the results using the flow chart and have the class chart each group's result.
• Pass out one rock at a time to each group and allot 5 minutes to test, discuss and decide on its rock name. After 5 minutes, ask questions from the flow chart to guide students to the correct rock name and chart the results.

3. Provide students with some information to classify the rocks as sedimentary, igneous or metamorphic, such as a textbook, website material or verbal explanation.
4. Have students refer back to the Alabraska map and have them identify the best area for their cavern to be built while referring to their worksheet answers. 
5. Lead a concluding class discussion to review students' answers to the the worksheet questions, as described in the Assessment section.

Assessment

Worksheet & Data Table: Review students' data and answers on the Rock Test Data Table and Rocks, Rocks, Rocks Worksheet to gauge their mastery of the concepts. Refer to the Rock Lesson Answer Key for example data table and worksheet answers.

Concluding Class Discussion: After testing and recording is done and students have completed the worksheet questions, which are intended to give meaning and context to the rock properties, lead a class discussion to review those answers. Discussing the answers is beneficial to the overall project and to students' retention of rock property descriptions. Also ask students:

• Why is it important to know rock properties before you build in it?
• How might these characteristics affect your cavern? (Possible answers: A soft rock might cave in, an extremely hard rock might be too difficult to drill through, a porous rock might let water flood the caverns, etc.)
• What is one way in which igneous rocks form?
• What is one way in which sedimentary rocks form?
• What does metamorphic mean?

Activity Extensions

Have students find geology maps for their state and determine the most common rock types present in their state or region. Applying their findings in this activity, have them determine the best locations to build caverns in their state.

Activity Scaling

For younger students, have the teacher do the testing in the front of the classroom (more of a class demo), asking questions from the flow chart. Then talk students through charting the results.

Copyright

Supporting Program

Acknowledgements

Adventure Engineering was supported by National Science Foundation grant nos. DUE 9950660 and GK-12 0086457. However, these contents do not necessarily represent the policies of the National Science Foundation, and you should not assume endorsement by the federal government.