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Chapter 3 released on YouTube

Chapter 3 is all about symmetry. We will start with the symmetries that can be found in everyday objects.

You will then learn how to classify crystals into their respective classes. We have prepared a small poster, so you can keep track of your very own collection of crystals.

Furthermore, we want to begin to talk about translational symmetry. This symmetry is a particular feature of crystal structures with their repetitive patterns.




Example – Thenardite, Na2SO4

Named after the French chemist, Louis Jacques Thenard (1777-1826).

Anhydrous sulphates. I: Refinement of the crystal structure of celestite, with an appendix on the structure of thenardite

Hawthorne F C , Ferguson R B
The Canadian Mineralogist , 13 (1975) p.181-187




SO4 tetrahedra (yellow)
Na (green)

3D rotatable model of Thenardite