One of the more visually spectacular types of slides prepared in Victorian times were the preparations of crystallized chemical compounds for viewing between crossed polarizing filters (Polariscope). A large selection of these slides were produced by all the commercial preparers, and they still amaze and entertain with their instant transformation when viewing, from drab and colourless, into a kaleidoscope of colour and form with the rotation of the polar filter. The addition of a thin Selenite crystal in the light path between the polarizing filters, enhances the available colour variations.

Crystallized Aniline in polarized light with Selenite filter

Various Crystallized Chemical Compounds in polarized light with filters; above, crystals of Sulphate of Strontium, and below, 3 variations of Salicine crystal mounts by J.T. Norman, with one imaged below.