# Understanding Crystal Symmetry via Gestures

## Summary

In this exercise, students use a small mirror to explore the meaning of mirror symmetry, and then use their hands to gesture mirror planes for a group of familiar objects. They also explore the rotational symmetry of a group of familiar objects, and then use their hands to gesture the rotational axes and rotation. Finally, they use gestures to show mirror and rotational symmetry of wooden crystal models.

## Learning Goals

After successfully completing this exercise, students will be comfortable using gesture to convey information about planes of symmetry and axes of rotation, and will have a firm understanding of how those concepts relate to mineral symmetry.

## Context for Use

This exercise is intended for use when students are first introduced to mirror and rotational symmetry for minerals. It could also be used to review those concepts. Because students are actively gesturing mirror and rotational symmetry elements, it allows the instructor to identify any students who are struggling with these concepts, and to help them.

## Description and Teaching Materials

Students gesture the mirror and rotational symmetry elements of a variety of familiar objects and of wooden crystal models. Each pair of students gets

• half of an eraser,
• 7 cans or spheres (e.g. ping pong balls, tennis balls, or Styrofoam balls),
• an old-fashioned 6-sided pencil,
• some dice of various shapes (you can order gaming dice online from a variety of sources, or look for a store in your area that sells board games),
• a small mirror, and
• wooden block models of crystal shapes.

Student handout: Mineral symmetry gesture exercise (Microsoft Word 56kB May12 15)

## Assessment

The instructor walks around the room and verbally quizzes students as they are doing the exercise to assess their understanding.

## References and Resources

Goldin-Meadow, Susan (2011). Learning Through Gesture. Wiley Interdisciplinary Reviews: Cognitive Science, v. 2, n. 6, pp. 595–607.

Using Gesture to Support Spatial Thinking highlights the value of gesture in communicating spatial information. It consists of two short exercises, and can be used in preparation for any other exercise in which students will be asked to use gesture to communicate spatial information.