Summary:

In this lesson students categorize minerals according to texture, cleavage, color, luster, and hardness, with a focus on hardness. They develop their own hardness scale and later compare it to the Mohs scale. They record their findings in their science journals and on graphic organizers. They share their results with the class.

Learning Goals / Objectives:

The students will demonstrate an understanding of how minerals are classified according to color, luster, texture, and hardness.
The students will record, analyze, and present data in written, oral, and graphic form.

Background

Part of science is categorizing the world around us. Scientist constantly group plants, animals, rocks, minerals, and etc. according to their physical properties. One method that geologists use for identifying minerals is using the Mohs scale of mineral hardness. In 1812 Friedrich Mohs came up with the idea and practice of comparing minerals by seeing which mineral can scratch others. The Mohs scale is commonly used today to compare and identify minerals. Minerals are pure substances that are found in nature. Rocks are made up of many different minerals. On the Mohs scale talc is considered the softest mineral and is given a rating of one. Diamond is rated 10 because it is, or was at the time, the hardest mineral. All other minerals fall in between the two. To use the scale the hardest substance a mineral can scratch is compared to the softest. The rating is then calculated to fall in between the two. Other physical aspects of minerals include color, texture, and cleavage.

Setup:

Have a tray of paperplate containing a sample of each mineral, unmarked, ready to distribute. On each plate also have a paperclip, tile, penny.. Each group will also need a copy of the Mohs hardness scale.

Anticipatory Set:

Hold up an apple and an orange. Ask the students “Tell me something about these.” Call for responses. Tap them on the table and rub their surfaces to encourage more in depth responses. Discuss with students that scientist like to classify objects according to various physical properties. List some prosperities on the board; hardness, color, texture, and luster. Have them describe the apple and orange according to these traits. Introduce the idea of cleavage by physically, it may take some effort, ripping the apple and orange in 1/2. The orange will split on a segment and the apple will be a soggy mess. Tell the students that when you break minerals they split in similar ways. This is called cleavage. Add cleavage to the board and have the class describe the oranges and apples cleavage.

Instructions / Activities:

1. Step 1 Info. Introduce the lesson with the set. Have students get out science notebooks and clear desks. Pass out minerals to each group. Allow them a few minutes of free exploration and discussion about the minerals.

2. Step 2 Info. Ask, “How can we describe these minerals according to the physical aspects we have listed on the board?” Have students make a team chart and individual charts in their science notebooks. Tell them that we will consider hardness later.

3. After they have categorized the minerals according to color, texture, and cleavage, introduce the idea of hardness by returning to the apple and orange. Take a new apple and smash an orange with it. Ask, ” haow can we test the hardness of the minerals?” Introduce the idea of the scratch test.

4. Have students put the minerals in order from softest to hardest by scratching one against the other. This may take some time, and will involve critical thinking skills. Keep it open ended and let them solve it on their own. Do stop the process and describe the difference between a streak and a scratch. Project them both up on the doc-cam. A streak you can rub off with your finger and a scratch leaves a groove.

5. Have them test their results with the paperclip, penny and fingernail. Their fingernail should only scratch the Gypsum. The penny will scratch the Gypsum and Calcite and the paperclip can only not scratch the quartz.

6, The students now record their results on their graphic organizers, both in their journals and on the team charts. Have them present their findings.

Assessment:

Formative assessments include:
Class discussion
Journal entries
Individual and team interviews
Two mystery minerals at a back table for individual exploration, with teacher observation and prompting,
An “I know…….because….” writing, drawing, or etc.

Summative assessments include.
Test; written short answer, multiple choice, and matching.
Vocabulary test.

Wrap-up / Closure:

Pass out one apple and orange to each group. Have them catagorize, cleave, share, and eat them.

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