Courses: P14, P16, P41, P47
This crystal polarizes light, coming from the image below it, in two orthogonal orientations, each one slightly shifted in space. Making it impossible to read text, for instance. If you hold polarizing film above it you can orient the film to select one image or the other, either of which is perfectly clear.
Setup: The best way to display this is to place a transparency with text on it above a light box. Place the crystal on the text, and use a camera (a doc cam will do nicely) to display it on a projector. You can also use a metal plate with a small hole in the center; the hole will appear to be two holes, slightly offset from each other, when viewed through the crystal.
