Most children have picked up a rock or mineral to show their parents or friends. Some children may even have found a crystal or fossil. Children often collect and sort rocks and minerals; they also may trade them with friends. They are fascinated with the colors, sizes, and textures of rocks and minerals they find as well as of those they see in museums and rock shops. This natural interest, coupled with the variety of rocks and minerals, leads many children to wonder what these earth materials are made of and how they were formed.

Rocks and Minerals is a 16-lesson unit in which third-graders investigate rocks and minerals to answer these and other questions. Students explore the similarities and differences among rocks; they also study how rocks and minerals are both similar and different. They conduct several tests on minerals and develop a systematic way to record their observations. Finally, students apply the information they have collected to identify the minerals they have been studying by name. These activities introduce students to the way geologists study rocks and minerals. They also help students develop and apply process skills in observing, describing, and recording.

Lesson 1 begins with a class brainstorming session during which students share what they know about rocks and the questions they have about them. As they observe and describe three rocks, students are introduced to one of the key concepts of this unit--that rocks have different properties. This lesson serves as a pre-unit assessment of students' present thinking about rocks. It also provides baseline information that the teacher may use to assess students' observing, describing, and recording skills.

In Lessons 2 and 3, students explore the properties of the three rocks they examined in Lesson 1 as well as nine new ones. After sorting these rocks on the basis of their observable properties, they read about where rocks are found and how they are formed. The reading acquaints them with the concept that rocks can change as a result of heat or pressure. The experiences in these two lessons deepen students' appreciation of the diversity of rocks.

Lesson 4 broadens the students' investigations of earth materials by introducing them to minerals. After exploring three mineral samples, students examine their rocks with a hand lens and look for small pieces of minerals. Through this experience, students are introduced to the concept that minerals are the "building blocks" of rocks.

In Lesson 5, students receive a set of 12 minerals, labeled "A" to "L". They examine the minerals and discuss their observations with their partners and classmates. Students also share what they know about minerals and the questions they have about them. This activity provides a second opportunity to assess their prior knowledge.

In Lessons 6 to 12, students explore the minerals to learn more about their properties. They perform a series of physical and chemical tests, called "field tests", that geologists use to identify and classify minerals. The students describe their results to their partners and classmates and systematically record their observations on 12 mineral profile sheets. As they perform the tests, students have an opportunity to learn how to manipulate science materials. They also acquire new vocabulary related to the study of minerals.

The field tests that students perform are of varying degrees of complexity, beginning with simple tests and moving on to more challenging ones. In Lesson 6, students use their senses to explore the feel and smell of the 12 minerals. In Lessons 7 to 10, they move on to test and record the observable and identifying colors, transparency, luster, and hardness of each mineral. In Lesson 11, they test each mineral's magnetism. These explorations conclude in Lesson 12, where students focus on the shape of minerals. After each test, students read about one or two minerals that display a distinctive result for the test that they have just performed.

In Lesson 13, students review the information they have recorded on their mineral profile sheets and identify the properties that helped them learn the most about each mineral. After summarizing these properties, students examine and compare several samples of each mineral. These observations broaden their understanding that even though minerals share certain properties, individual samples can look quite different from one another. In Lesson 14, students compare the information they have recorded about each mineral with that provided by a geologist on mineral identification cards. Applying all the information they have accumulated, students match each mineral sample to the appropriate card and thereby identify the minerals by name. As a final activity, they combine their mineral profile sheets and the mineral identification cards to make their own "Minerals Field Guides".

In Lesson 15, students are challenged with an application assessment. They are given three "mystery minerals" and three blank mineral profile sheets. They apply the field tests of their choice to learn as much as they can about each mineral. Using all the information they have acquired during their exploration of minerals and their "Mineral Field Guides", students then compare the three new minerals with those they have studied previously.

The unit concludes by giving students the opportunity to make the connection between minerals and rocks and to explore their uses. Students learn that minerals are obtained from rocks. Using guided and independent research, they prepare reports on a rock or mineral that interests them. Students' oral presentations of these reports provide an opportunity for a final assessment of the knowledge they have gained from their study of earth materials.

Throughout Rocks and Minerals, students have many opportunities to observe the similarities and differences in properties of minerals and rocks and to gather, organize, and interpret data. They discover that the application of scientific techniques can provide them with useful information about rocks and minerals. As they perform the field tests and discuss the results, students become engaged in a process that encourages problem solving and fosters understanding of the concept that scientific results cannot always be reported with "yes-or-no" answers.