In this movie taken in plane-polarized light, we see numerous tourmaline crystals whole long axes are perpendicular to the stage, and one whose axis is in the plane of the stage. Note the different pleochroic behavior.
Here we see a more complex pleochroic scheme. This plane-polarized-light view is dominated by glaucophane. Note that although three colors are visible (yellow, blue, and purple), any individual grain only shows two of the three as it rotates around.