Atlas of Optical Crystallography Interference figures part IV

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

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

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

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

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

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

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

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

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

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 224 12 84 plates, 1 plate, each 24/812/8 6/8 3/8 2/8 1/8 λ thick λλthick Olaf Medenbach, Ruhr-Universität Bochum

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

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

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

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. Olaf Medenbach, Ruhr-Universität Bochum