Krüss polariscope refers to gemmological polariscopes manufactured by A. Krüss Optronic GmbH of Hamburg, a precision optical firm founded in 1796. The standard Krüss polariscope is a benchtop instrument with a built-in light source, two crossed polarising filters mounted on the upper and lower stages, a rotating stage for sample positioning, and an optional conoscope lens for interference figure observation.

The instrument is used for the routine determination of optical character, distinguishing isotropic species (diamond, garnet, spinel, glass, amorphous opal) from anisotropic species (corundum, tourmaline, beryl, topaz and most other gem minerals), and within anisotropic stones, separating uniaxial from biaxial behaviour through the conoscope. Anomalous double refraction, ADR, in nominally isotropic stones is also examined on this class of instrument.

Krüss polariscopes compete in the European market with Eickhorst, GIA-branded equipment and various Asian-manufactured budget models. They are well-built, robust enough for daily laboratory use, and supported by spare parts availability through the firm's Hamburg facility. The diagnostic logic and procedure are identical to those used with any other manufacturer's polariscope.