Hand-held polariscope, 19th century.
© Science Museum / Science & Society Picture Library
This hand-held polariscope is a demonstration device to show how thin sections of different minerals look when viewed in polarised light. A selection of seven mineral samples are mounted on a rotating wheel so that each can be examined using an eyepiece fitted with a polarising material such as Iceland spar. As each sample is pased in front of the polarising eyepiece the light's intensity will vary greatly indicating different types of crystal structure. Made from turned rosewood the sample wheel carries labels for each mineral. The samples are viewed in turn through a slotted opening in the handle of the instrument.