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Netherlands Gemmological Laboratory

Identification and grading services to jewelers, auction houses, dealers, and consumers.


Post address
Netherlands Gemmological Laboratory 
P.O. Box 9517 
2300 RA Leiden
The Netherlands

E-mail: nel@naturalis.nl

Telephone: +31 (0)71-7519 687 / +31 (0)71-7519 661 / +31 (0)71-7519 665


Reports of the Netherlands Gemmological Laboratory are issued on diamonds, colored gemstones and pearls. Diamonds are graded according to international standards; the weight in carats, the color, clarity, and quality of the cut are evaluated.

All these factors are important when the value of a particular stone has to be established. As diamond is a valuable commodity, it is frequently simulated by oher products, like synthetic cubic zirconia and synthetic moissanite.

Other gems, like ruby, sapphire and emerald, are frequently treated to enhance their appearance (color and/or clarity), but also synthesized or simulated. 
So for each gemstone various categories exist, each representing a different value, for instance ‘natural ruby’, ‘enhanced ruby’, ‘treated ruby’, ‘synthetic ruby’ and imitation of ruby (often glass).

In view of the difficulties in describing and identifying a gemstone correctly, the Netherlands Gemmological Laboratory is frequently asked for advice. The Lab is independent and not involved in trading. It can therefore give an objective description and scientifically sound opinion on the quality and, where possible, provenance of any gem material that is offered for examination. The reports issued are internationally recognized and do not include a valuation.

In addition to relatively simple instruments used in earlier days, such as a refractometer, polariscope, and microscope, the laboratory (like other major gemmological laboratories in the world) now houses more advanced technology like Ultraviolet-Visible (UV-VIS) and Fourier Transform Infrared (FTIR) spectrometers, to measure absorption (or transmission) spectra of gemstones in the ultraviolet, visible and infrared frequencies, and energy dispersive X-Ray Fluorescence (micro-EDXRF) for non-destructive chemical analysis of gemstones. Additionally, radiography and X-Ray Diffraction techniques are used for pearl testing.

Other activities include public lectures and various courses and seminars designed for professional jewelers and others, also in cooperation with the School for Gold- and Silversmiths and Jewelers (Schoonhoven). There is a strong link between the Lab, the collections, research, and public activities. The historical collections (e.g., gems donated by King William I) provide invaluable reference material for natural gemstones.

Services offered

The reports may include information on: 

Reports are generated in English or in Dutch, and are in line with international guidelines and rules, according to The World Jewellery Confederation (CIBJO) and the Laboratory Manual Harmonisation Committee (LMHC).

Read more about the Netherlands Gemmology Laboratory (in Dutch).