An introduction to minerals and rocks under the microscope
An introduction to minerals and rocks under the microscope

This free course is available to start right now. Review the full course description and key learning outcomes and create an account and enrol if you want a free statement of participation.

Free course

An introduction to minerals and rocks under the microscope

2.2.1 Isotropic and anisotropic materials

Materials that have the same atomic structure in all directions are termed isotropic. When light passes through such a material it doesn't matter in which direction the light vibrates, its speed (and therefore the refractive index) is the same. This is true of light passing through air, water, glass and some minerals.

  • To which crystal system would you expect an isotropic mineral to belong?

  • The cubic system, because it defines materials for which the crystal structure and, consequently, its optical properties are the same along each crystallographic axis.

Minerals belonging to other crystal systems are more common than those with cubic symmetry. They have internal structures that are not the same along all crystallographic axes and are therefore anisotropic minerals. The importance of this is that the behaviour of the light passing through an anisotropic crystal depends on the vibration direction of the light and its relationship to the crystal structure.


Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to university level study, find out more about the types of qualifications we offer, including our entry level Access courses and Certificates.

Not ready for University study then browse over 900 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus