Distinguishing gemstones from glass

Polariscopes facilitate the rapid detection of common gemstone imitations, such as glasses or synthetic spinels. For the investigation of precious stones and gemstones – as well as syntheses or imitations – these are positioned on the rotatable glass plate above the polariser. The materials to be investigated are positioned between the polariser and the analyser and can be moved with the glass plate. Illumination is from below and the materials are viewed from above. This involves rotating the stone lying on the polariser or held between the filters.

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Tips for working with the polariscope

When working with polariscopes, the best results are achieved if the stones to be investigated are also embedded in glass vessels with immersion media. If the polariser and analyser are turned exactly 90° against each other for the dark position, the background of the stones is black.

Application of polariscopes

If the stone in the dark position of the polariscope shows four times bright and four times dark when rotated 360 °, it is identified as an anisotropic stone. In this case, it could be a red gem such as ruby or tourmaline. In the case of a ruby, however, it must be taken into account that a synthetic ruby can also be present. If dark bars move through the stone when turning, this speaks for simple glass.

The inner structure is responsible for the different modes of appearance. Natural or synthetic non-organic materials have a regulated internal structure on an atomic scale, which is known as the crystal lattice or crystal structure. Glasses, on the other hand, are largely disordered, they are amorphous. In the case of transparent materials, such as precious stones and other minerals, a distinction is made between so-called single-refractive (isotropic) and double-refractive (anisotropic) materials and special cases.

How polariscopes analyze gemstones in practice

See how easy polariscopes are to use and how the analysis works: The device immediately shows the optical behavior of the stone. Whether polished or rough – even several stones can be tested at the same time. Various polariscope models are available in the KRÜSS store for gemmology.

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Note: The gemstone refractometer is also a central component of ourlarge mobile gemstone laboratory, which stands for maximum flexibility. Each of the two mobile gemmological laboratories is equipped with high-quality, professional analytical instruments and enables precise investigations on the move – at trade fairs, at customers’ premises or directly on site.

Do you want to read more?

There are many other examination methods with the polariscope and a wide variety of appearances with which the inner crystal lattices or crystal structures can be observed.

We have compiled a large selection of relevant specialist information with many interesting detailed photos and descriptions of the basic examination methods in a free white paper. This specialist publication was produced in collaboration with Prof. Dr. Jochen Schlueter wrote. He is a qualified mineralogist and is responsible for the permanent collection of the Mineralogical Museum in Hamburg.

Here you can order the free white paper “Polariscope”, which describes many examination options with the polariscope. Simply enter your contact details here and we will send you our detailed whitepaper as a PDF by email.

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