Comparing Quartz Polymorphs

After successfully completing this exercise, students will be able to

• Make a visual comparison of two similar crystal structures.
• Describe key differences between the structures of low-temperature and high-temperature forms of quartz.
• Relate atomic structure to symmetry and crystal systems.

Although the apparent focus of this exercise is on the structures of two polymorphs of quartz, it is also about getting students to observe the finer details of crystal structures. It can be used to develop students' attention to detail, whether or not the effect of temperature on the structure of quartz is of particular interest.

Students compare the structures of low-temperature and high-temperature polymorphs of quartz in detail, looking at virtual models of the structures from three different perspectives (viewed down each of the crystallographic axes). They are then asked to relate the structural differences to symmetry and crystal systems.

Quartz polymorphs exercise (Microsoft Word 2007 (.docx) 427kB May12 15)

If students have difficulties understanding polyhedral diagrams of minerals, they may find it helpful to complete the Polyhedral Diagrams exercise prior to this one.

Student learning is assessed by grading their answers to the questions on the worksheet.

The images in this exercise were created using CrystalMaker software. This software allows students to examine and manipulate virtual 3D crystal structures. It is a great learning tool if your department can afford a site license.