The first photo shows the sample backlit with a flashlight and subsequent photos are under ambient lighting conditions.  The video illustrates the behavior of this sample in a polariscope.  The video starts with viewing the sample in plane polarized light.  Rotating the crystal in this view demonstrates pleochroism, but this view is not looking along the plane of the a-crystallographic axes.  Maximum pleochroism is observed when viewed along the plane of the a-crystallographic axes after the crystal is reoriented.  The pleochroism goes from blue to yellow and is quite distinct!  We then change the orientation of the crystal to look along the c-crystallographic axis in plane polarized light.  Rotating the crystal in this plane doesn't really demonstrate pleochroism, although I don't do the best job in the video of keeping everything steady.  Although it isn't shown in the video, you can use views with crossed polarizers to help identify the pleochroic endmember colors associated with epsilon and omega and also determine extinction angles.  

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