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 many amateurs, 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 simple rotation of a polar filter. The addition of a thin Selenite crystal or other wave modifying plate in the light path between the polarizing filters, enhances the available colour variations.

Above, a selection of crystallized chemical mounts by 3 of the most successful Victorian age slide makers... (l to r)  early C.M. Topping,  J.T. Norman,  E. Wheeler, and later C.M. Topping. All were made to be viewed between crossed polar filters (Polariscope).

Crystallized Aniline in polarized light with Selenite filter

Above, a selection of crystalline mounts, obviously all by the same maker (currently unidentified). All specimens are pharmaceutical compounds, which possibly suggests the makers occupation.  Also note econdary retailers label from T.H. McAllister, New York.

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

Above, detail of crystalline compound Platino~cyanide of Strontium imaged in Polarized light.  Below, a chemical mount of Potassium Chloride by A.C. Cole with images taken from the slide with crossed Polar filters (Polariscope).