1. Olaf Medenbach, Ruhr-Universität Bochum Atlas of Optical Crystallography Olaf Medenbach Institut für Geologie, Mineralogie und Geophysik Ruhr-Universität Bochum 44780 Bochum, Germany olaf.medenbach@rub.de © by Olaf Medenbach Interference figures, part IV: special features, anomalous and disturbed figures

2. Olaf Medenbach, Ruhr-Universität Bochum Calcite inactive, black isogyre cross Quartz, 1mm, active Interference Figures of optically active crystals

3. Olaf Medenbach, Ruhr-Universität Bochum Quartz, 1mm Quartz, 4mm Interference Figures of optically active crystals

4. Olaf Medenbach, Ruhr-Universität Bochum Interference Figures of optically active crystals Change of interference figure on rotation of the analyzer The animation starts a few seconds after the next click.

5. Olaf Medenbach, Ruhr-Universität Bochum Interference Figures of optically active crystals Quartz single crystal, 1mm thick Composite section with right and left handed quartz superimposed: Airy spiral

6. Olaf Medenbach, Ruhr-Universität Bochum Interference Figures of optically active crystals Airy spirals in quartz Left handed on top Right handed on top

7. Olaf Medenbach, Ruhr-Universität Bochum Quartz, normal interference colors Apophyllite, abnormal interference colors Abnormal Interference Colors on a Wedge inverse colored isochromes due to anomalous dispersion of the birefringence

8. Olaf Medenbach, Ruhr-Universität Bochum Calcite, normal colors Benzil-l, abnormal colors and, in addition, optical activity Abnormal Interference Figures inverse colored isochromes due to anomalous dispersion of the birefringence

9. Olaf Medenbach, Ruhr-Universität Bochum SrS 2 O 6 4H 2 O Apophyllite "Leucocyclite" Abnormal Interference Figures inverse colored isochromes due to anomalous dispersion of the birefringence

10. Olaf Medenbach, Ruhr-Universität Bochum Mica-combination after Nörrenberg a systematic stacking of biaxial crystals results in an uniaxial interference figure – in nature this is realized in twinned biotite crystals 1 plate, 24/8 λ thick2 plates, each 12/8 λ thick4 plates, each 6/8 λ thick8 plates, each 3/8 λ thick 12 plates, each 2/8 λ thick24 plates, each 1/8 λ thick

11. Olaf Medenbach, Ruhr-Universität Bochum Disturbed Interference Figures disturbed figures on a twin lamellae in calcite

12. Olaf Medenbach, Ruhr-Universität Bochum Disturbed Interference Figures disturbed figures on a twin lamellae in diopside

13. Olaf Medenbach, Ruhr-Universität Bochum both crystals of almost the same thickness crystals of different thickness Disturbed Interference Figures disturbed figures on a twin lamellae in aragonite

14. Olaf Medenbach, Ruhr-Universität Bochum Absorption Brushes in Pleochroic Crystals Epidote, almost perpendicular to one optical axis between crossed polarizers in unpolarized light The animation starts a few seconds after the next click.