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Content of the article

  • Coloring
  • Irradiation
  • Diffusion treatment
  • Heating
  • Impregnation and crack filling
  • Natural gemstones
  • The certificate as a seal of quality

As in many areas of life, it was discovered early on in the case of gemstones that the quantity of "beautiful" gemstones that nature supplies cannot satisfy worldwide demand. Accordingly, many precious and gemstones have had their natural characteristics altered by technical intervention to enhance their quality in color, transparency and strength. Specific treatments give rough stones with blemishes a chance to meet apparent quality standards

However, some treatments are not desirable. To ensure buyer protection, the International Association for Jewelry, Silverware, Diamonds, Pearls and Gemstones (CIBJO) has developed worldwide rules for the trade. Accordingly, all treatments on a gemstone must be clearly declared

Natural stones can be treated with the following methods:


In order to increase the color intensity of gemstones, there are various declarable methods to artificially color the natural stone. In the past, gemstones were coated with color paints or varnishes. However, this method has become obsolete. More common now is the vaporization of the gemstone surface with ultra-thin metals, such as titanium or gold. The treatment is easily visible under a microscope and due to the extremely thin layer thickness, the adhesion of the color is not long-lasting


An improvement or total change in the color of a gemstone can be achieved by irradiating it with high-energy electromagnetic rays or by shooting it with elementary particles. This method is mainly used with topazes. However, electron irradiation is also common for morganites. It is important with this treatment method that the irradiated gemstones are first stored after treatment so that any residual radiation can decay. According to the U.S.NRC (United States Nuclear Regulatory Commission), wearing irradiated gemstones is safe. 

Diffusion treatment

To give pale or almost colorless stones a more intense color, a so-called diffusion treatment can be applied. In this process, a coloring foreign substance (e.g. titanium or chrome) is introduced into the first surface layers of the stone by means of a high-temperature treatment. The disadvantage with this manipulation method is the low penetration depth. The artificially created color can lose its intensity or even disappear completely through polishing or grinding. 

GEMHYPE.COM does not offer such stones. 


Inconspicuous specimens can be improved in color by heat treatment and assigned to a higher price range. The heating of gemstones is a common and accepted method in the gemstone industry, which is often practiced because it causes many advantages. The color of the stone remains resistant to UV rays, it can be easily polished and the color change happens throughout the stone, unlike diffusion treatment with low penetration depth. 

Heating brings the color already contained in the stone to its full development. The duration of the heat application can take only a few minutes, but it can also take several hours. It depends on the type of gemstone and the desired color effect. Low temperature treatment is carried out between 250 and 600 degrees Celsius. Thermally treated corundum is even heated between 1,200 and 1,900 degrees Celsius. This method is used for the majority of transparent gemstones on the market, such as amethyst, aquamarine, morganite and tanzanite. Some gemstones would not exist as gemstones without firing, such as tanzanite or starlite.

Impregnation and crack filling

In this type of treatment, gemstones are mixed with substances to fill cracks and pores. This visually creates a higher intensity in color, purity and stability. Since ancient times, stones have been treated with colorless oils to fill cracks and make them unrecognizable to the naked eye. Since this treatment can be reversed, nowadays resins are also used to achieve a more durable result.

Natural gemstones

Thus, a gemstone may be called "untreated" only if its nature has been created exclusively by Mother Nature, without any technical intervention, and its appearance has been changed only by cutting and polishing. exhibits untreated gemstones in its online store. Besides, we offer only gemstones treated by heating or by gamma or electron irradiation. We do not work with impregnation, crack filling, diffusion treatment and coloring at and HC Arnoldi. 

Click here for our untreated gemstones.

Click here for our heated gemstones.

Click here for our electron irradiated gemstones. 

We stand for quality with transparency. In our glossary for colored gemstones and glossary for diamonds we give a defined description of the treatment methods of our gemstones. In our product views you will always find a detailed product description. Likewise, customers are usually interested in buying only untreated gemstones, as in the case of morganite. Therefore, we offer the possibility to filter for untreated, heated or electron-irradiated gemstones

The certificate as a seal of quality

Since a treatment can change the value of a gemstone, the method used must be clearly recognizable to the buyer. A certificate issued by an internationally recognized gemstone laboratory, such as the German Gemmological Institute (DGemG) in Idar-Oberstein, serves as proof of the accuracy of the treatment details and the natural purity.

If desired and depending on the value of the gemstone, a certificate verified by the DGemG can be requested from However, the costs for this are to be borne by the customer.

As a specialty store, we can of course also offer an in-house certificate. Would you like to have a certificate issued at the time of purchase? Contact us and we will issue a certificate upon request!

If the value of the goods is less than 500 Euro, we charge 19.90 Euro for the certificate. From a value of goods in the amount of 500 euros, the certificate is free of charge.


Book: Edelsteine und Schmucksteine, Author: Walter Schumann, Publisher: blv

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