Phosphorescent pebbles are presented in the market as natural rounded pebbles (3.53 density) possessing extraordinary properties such as green phosphorescence when exposed to a strong light source and patchy blue to green fluorescence in short- and long wave UV-light (Figure 1), again with green phosphorescence (no blue). Such items appeared multiple times in the last […]
Introduction In May 2015, the author (AP) was made aware that a company in Thailand (Tairus Co. LTD, Bangkok) had commissioned to a laboratory in Russia the production of new types of synthetic spinel of “lavender” colors by the method of crystal pulling from flux. This technique is the same used at the Institute of […]
Introduction Cobalt-spinels are considered one of the most precious spinel and are rarely colored blue with or without grey to black tones. Blue Cobalt spinel are at least 10-100x more expensive per carat than grayish-blue colored spinel. Cobalt intensifies the blue color in spinel, considerably enhancing its beauty. Cobalt-spinel over 5ct can be 10,000 to […]
We would like to inform our customers that rubies found to be unheated when tested by GRS are sometimes heated after certification and presented as natural unheated rubies to the market without re-certifying with GRS. This very low temperature warming does not require repolishing of the stone and therefore no weight loss and no dimension […]
CVD-grown Blue Diamonds – Identified by GRS and CGL-GRS laboratories Hong Kong, Lucerne and Vancouver – A distinctly new type of synthetic blue diamond sized from 0.25 carats to over 1.25 carats turned up at both the Bangkok and Hong Kong Gems & Jewellery Fairs in September 2013 along with pink, yellow, and colourless varieties of […]
A large number of diffusion-treated stones are detected in the laboratory. The diffusion-treatment includes the well-known method of adding Titanium in the surface. Some of the material has been additionally Beryllium-treated. The new aspect of this treatment is that the treaters obviously select already heat-treated sapphire with internal blue color-zoning. Than the stones are diffusion-treated […]
By Dr. A. Peretti and W. Bieri For the last couple of years, the appearance of lead-glass treated rubies has been widely recognized in the trade. The treatment is primarily used to enhance clarity in rubies or pink sapphires of lower commercial value. This treatment has been regularly seen at the GRS laboratory in rubies […]