Testing Rocks and Minerals

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Objective

SWBAT describe ways to test rocks and minerals based on Mohs Hardness Scale and other physical properties used by geologists.

Big Idea

Hardness, color, streak, luster, and cleavage are physical properties that we can test!

Teacher Preparation

In this lesson, students learn about the different tests of physical properties of rocks and minerals, including Mohs hardness scale, luster, and streak. This lesson aligns to Essential Standard 1.E.2.1, Summarize the physical properties of Earth materials, including rocks, minerals, soils and water that make them useful in different ways.

The essential question I post for today is, "How do geologists test rocks and minerals?" Listen to my Explanation of Essential Standards and Essential Question.

 

Materials:

*1 mineral per student (They could share!)

*Tools for testing - paper clips, unglazed ceramic tiles (I ordered mine from Google), pennies

*1 Mineral Recording Sheet per student

Warm Up

10 minutes

As we begin this lesson, I read the essential question for today to my students and then I say,

"There are so many different minerals. How do you think geologists can tell each mineral apart?"

After a few responses, I say,

"Today we are going to learn about some tests that geologists use to sort and study minerals".

First, we look together at this website that lists the physical properties of minerals.

As we go through the website, I create an anchor chart titled 'Physical Property Tests' and list cleavage, hardness, luster, streak, and color and a brief description of how each test is done. I also add the printed picture of Mohs hardness scale for reference to the anchor chart.

 

Activity

25 minutes

To get students asking questions about the tests before this activity so they are fully engaged, I say,

"If you were a geologist and you found a mineral, what are some questions you might ask?"

This should be supported by the anchor chart we created about the tests. Asking scientific questions that can be answered by scientific investigation supports Science and Engineering standard 1.

Students are going to try some of the tests out for themselves today. I say,

"Today, you and a partner are going to work together to identify some of the physical properties of some minerals by doing these tests yourself. You can identify cleavage, which is a break or ridge in the rock, by looking at it carefully. Let me show you how to identify the streak, which is the actual color in the mineral that sometimes you cannot see just with your eyes".

I use an unglazed ceramic tile and explain mineral streaking to show my students how to do it. I also tell them to hold the tile carefully, flat on the table, because the tiles can break.

Then I explain how to test for hardness using Moh's Scale and scraping the mineral with your fingernail (2.5), a penny (3) and a nail (6). I show this video to further explain this test.

After I explain each test, I give each student a mineral and a chart for them to record their data, as well as the tools they need to test their minerals.

As students work, I circulate to make sure everyone is using the tools safely and I help where I am needed. I also listen for misconceptions and ask questions to further student's thinking about the minerals and tests. Students also work together, and I hear one student explaining Mohs to several others, so I make him an expert!

This investigation supports Science and Engineering Practice 3, Planning and Carrying Out Investigations as students make first hand observations and collect data that can be used to make comparisons and answer their questions. Students are also recording information, their observations and ideas, which supports SEP 8.

Wrap Up

5 minutes

After students have completed their Mineral Recording Sheet and finished their investigation, I ask them to bring their minerals and their recording sheets to the carpet and sit knee-to-knee with another group. I tell them that they have 2 minutes to share the information about their mineral and to compare the two minerals.

This time to communicate is really important as it fosters the enthusiasm for science and makes them want to learn about other rocks and minerals. This supports Science and Engineering Practice 8, evaluating and communicating information.

After a few minutes, I say,

"Who can answer the essential question for today? How do geologists test minerals - and why?"

Ending with the essential question leaves the focus on today's purpose and makes sure that everyone understands why we are testing the rocks and minerals.