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

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

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.

S276_1

Take your learning further371

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 courses372.

If you are new to university level study, we offer two introductory routes to our qualifications. Find out Where to take your learning next?373 You could either choose to start with an Access courses374or an open box module, which allows you to count your previous learning towards an Open University qualification.

Not ready for University study then browse over 1000 free courses on OpenLearn375 and sign up to our newsletter376 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 prospectus371