The gemstone refractometers allow direct determination of the specific refraction of light (refractive index) in cut stones. As the refractive index is a material constant that depends on the chemical composition of a material, it provides information about important features of a gemstone. Determination with a special gemstone refractometer is an easy-to-apply method. This method and a high-quality gemstone refractometer can be used to assess the authenticity and quality of a stone, for example. The gemstone refractometer is therefore part of the basic equipment of a gemmological and gemstone laboratory.
You need these products
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Anderson liquid FL100
89,00 €Contact solution for measurements with the gemstone refractometer to determine the refractive index
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Gemstone refractometer ER601-LED
1.081,00 €Professional gemstone refractometer with high-end equipment, with LED illumination. For refractive index measurement, authenticity testing, stone quality classification
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Gemstone refractometer ER605
381,00 €Compact gemstone refractometer with good optical equipment and LED. For measuring the refractive index and checking the authenticity and quality of stones
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EMERALD, SPINEL, GLASS OR TOURMALINE?
A dark green, faceted stone is available for testing. It could be an emerald or synthetic green spinel, green glass, green tourmaline or chrome diopside. The stone to be tested must have a well-polished surface of at least 1-2 mm². To measure, a special contact liquid is applied between the stone and the measuring surface. The stone is then placed on the measurement prism, the lid of the gemstone refractometer is closed and the refractive index is read.
When observing without moving polarising filter, the refractometer shows only a shadow line by chance. Two shadow lines appear when the stone is rotated on the measuring surface. It is clear that this is an anisotropic stone, amorphous glass or the cubic, synthetic spinel is immediately eliminated through the shadow lines. The maximum value is at n = 1.65, the minimum at n = 1.62. Therefore, emerald (n = 1.56-1.58) is not an option for the stone measured.
The measured values speak for a completely different stone. The expert can also see that the stone is optically uniaxial, – that is, trigonal, hexagonal or tetragonal, – because when the stone is rotated, one of the shadow lines moves while the other remains constant. This information points to a very specific mineral as the identity for the ornamental stone you are looking for. It is a popular collector’s stone, some of which are even more valuable than diamonds. You can find the solution in our free refractometer white paper.
How the refractive index measurement works
Our premium gemstone refractometer impresses with brilliant optics and a bright, razor-sharp scale. It measures the refractive index of polished stones with the highest precision – indispensable for the reliable identification of gemstones, syntheses and imitations. Discover a sample examination and experience how the device is ready to use in just a few simple steps. You can find various refractometer models in the KRÜSS store.
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More InformationNote: The gemstone refractometer is also a central component of our large 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?
If you want to know which stone our example above shows and are looking for more specialist information, order the white paper “Gemstone refractometer”. The specialist publication also explains the refractometer investigation of the “distant vision method” or “spot method” in detail. The whitepaper was produced in collaboration with Prof. Dr. Jochen Schlueter wrote. a qualified mineralogist in charge of the permanent collection on display at the Mineralogical Museum in Hamburg.
Here you can order the free white paper “Gemstone refractometer”, which describes many examination methods. Simply enter your contact details here and we will send you our detailed white paper as a PDF on the subject of “Gemstone Refractometers” by email.