Click in one of the buttons on the right side of the figure to operate one of the three symmetry classes of the orthorhombic crystal system on a face pole in stereographic projection. Among the 32 point groups of symmetry elements in crystallography the roups  2m,  22 and 2/mm belong to the orthorhombic system.The first group has mirror plane containing a 2-fold axis. The class (or group) 22 has a couple of 2-fold axis. The third is arranged  with a mirror plane perpendicular to he 2-fold axis and another mirror plane containing this axis.

A click on the circle will clear the figure and select a new face pole.

Exercise

1) At what angel one of the 2-fold axis intersects the other rotation axis in class 22?

2) At what angle the implicit 2-fold axis intersects the two announced rotation axis in class 22?

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