Dresden Green Diamondweighs almost 41 carats seen here in a hat pin.
The green colour is unique because of its natural radiation
( above )
The Dresden Diamond is being used to compare natural versus lab-produced green diamonds — it is hoped that it can be used to devise a test to differentiate between naturally green diamonds, which are extemely rare, and lab-produced ones.
This diamond is located in the Staatliche Kunstsammlungen Dresden, The New Green Vault.
This diamond is located in the Staatliche Kunstsammlungen Dresden, The New Green Vault.
SSEF develops a New Device for Type IIa Diamond IdentificationThe SSEF IIa Diamond Spotter™ and its Illuminator:De-colorization (!) of (brown) diamonds was proved to be feasible for high pressure/high temperature treated IIa diamonds (GE POL, Bellataire, see above).
The first step for an identification of such stones is the recognition of their IIa behaviour, i.e. transmission of short wave ultraviolet light. All type IIa (and rare type IaB) transmit short-wave ultraviolet (SWUV) light.. Most diamonds are type Ia and do not transmit SWUV.
The SSEF IIa Diamond Illuminator™ is an ideal light source for the detection of type IIa diamonds with the SSEF IIa Diamond Spotter™.
The SSEF IIa Diamond Illuminator™ is an ideal light source for the detection of type IIa diamonds with the SSEF IIa Diamond Spotter™.
Especially for the diamond trade the SSEF has developed the SSEF IIa Diamond Spotter™, a small instrument that works in connection with a short-wave ultraviolet light source. Ideally, the Diamond Spotter is combined with the new SSEF IIa Diamond illuminator™, a small portable 110/220V SWUV light source, which produces a monochromatic radiation of 254 nm. The screen of the SSEF IIa Diamond Spotter™ is made of a substance that fluoresces when exposed to a SWUV light source.
By placing a diamond into the Spotter and switching on the SWUV light source, the diamond will react by transmitting or absorbing the SWUV light, thus fluorescence or no fluorescence on the screen of the Spotter. In the case of a green fluorescent light spot on the screen, the diamond transmits SWUV and is thus of type IIa (or rare type IaB) and may have been "decolourised" by HPHT treatment. If no reaction, the colourless diamond is not a IIa diamond, thus not HPHT treated.
When a colourless IIa diamond is identified by its transmission of SWUV, the stone should be further analysed in a specialised gem laboratory (e.g., SSEF) where the HPHT treatment can be identified by Raman luminescence spectrometry.
The SSEF IIa Diamond Illuminator™ is sold with adapter and voltage converter by SSEF for US$ 500 or US$ 650 together with an SSEF IIa Diamond Spotter™ (plus shipment). The Spotter alone is US$ 150 (plus shipment). For further information, e-mail gemlab@ssef.ch
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Type of Diamonds
Natural Diamonds
Natural diamonds are classified by the type and quantity of impurities found within them.
Type Ia - This is the most common type of natural diamond, containing up to 0.3% nitrogen.
Clustered nitrogen atoms. Colourless to Yellow. 98% of all diamonds are Type Ia.
Type Ib - Very few natural diamonds are this type (~0.1%), but nearly all synthetic industrial diamonds are. Type Ib diamonds contain up to 500 ppm nitrogen. These diamonds about 0.1% prevalent.
Isolated Nitrogen Atoms. Orange, Orange Yellow to Brown.
Depending on the precise concentration and spread of the nitrogen atoms, these diamonds can appear deep yellow ("canary"), orange, brown or greenish.
Type IIa - This type is very rare in nature. Type IIa diamonds contain so little nitrogen that it isn't readily detected using infrared or ultraviolet absorption methods. No specific colour centre.
Yellow, Brown , Pink and Purple Type IIa diamonds have been documented. These diamonds are 1% to 2% prevalent.
These diamonds can be considered as the "purest of the pure" - they contain no, or minuscule amounts of impurities, are usually colourless, highly transparent and can be a higher colour grade than D.
Type IIb - This type is the rarest in nature. Type IIb diamonds contain no measurable amounts of nitrogen (even lower than type IIa) that the crystal is a p-type semiconductor.
These diamonds contain no nitrogen - but they contain boron, which absorbs red, orange and yellow light. These diamonds therefore usually appear to be blue, although they can also be grey or nearly colorless. All naturally blue diamonds belong to Type IIb, which makes up 0.1% of all diamonds.
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What about green diamonds?
Green diamonds are a separate case: these diamonds can contain clustered nitrogen atoms or they can contain no nitrogen atoms - what gives them their color is that they have been bombarded by nuclear rays during their growth. This bombardment makes them absorb magenta wavelengths, which gives them their green color. These diamonds are extremely rare.
The Dresden Green, named after the capital of Saxony where it was exhibited for almost two centuries, is certainly the most beautiful known specimen.
The first written trace of this diamond dates back to 1726: Baron Gautier, an evaluator in Dresden, refers in a letter to a green diamond that was proposed to King Frederic August I by a London merchant. Others say a Dutchman named Delles sold it to Frederic August II during a commercial fair in Leipzig in 1741. It is said that the rough stone was purchased in Golconda by the famous diamond merchant Marcus Moses, who would have had it cut in London shortly before 1741. Seized by the Soviets at the end of the Second World War, the Dresden Green was returned to the Germans in 1958. Today, it is kept in the Albertinium Museum in Dresden.It has a fancy green color, weighs almost 41 carats, has 58 facets and is cut in an irregular pear shape.
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Synthetic Industrial Diamonds
Synthetic industrial diamonds are produced the process of High Pressure High Temperature Synthesis (HPHT). In HPHT synthesis, graphite and a metallic catalyst are placed in a hydraulic press under high temperatures and pressures. Over the period of a few hours the graphite converts to diamond. The resulting diamonds are usually a few millimeters in size and too flawed for use as gemstones, but they are extremely useful as edges on cutting tools and drill-bits and for being compressed to generate very high pressures. (Interesting side note: Although used to cut, grind, and polish many materials, diamonds aren't used to machine alloys of iron because the diamond abrades very quickly, due to a high-temperature reaction between iron and carbon.)
Thin Film Diamonds
A process called Chemical Vapor Deposition (CVD) may be used to deposit thin films of polycrystalline diamond. CVD technology makes it possible to put 'zero-wear' coatings on machine parts, use diamond coatings to draw the heat away from electronic components, fashion windows that are transparent over a broad wavelength range, and take advantage of other properties of diamonds.
Additional Reading
Diamond - Molecule of the Month - This site covers the properties of diamonds, the differences between diamond and graphite, classification of natural diamonds, manufacture of synthetic industrial diamond, and chemical vapor deposition of polycrystalline diamond.
Links to Groups Studying CVD Diamond - The Bristol University chemical vapor deposition diamond group maintains this list of other groups engaged in similar research.
The Chemistry of Carbon - This article provides an overview of basic chemistry associated with carbon, emphasizing the crystallographic difference between graphite and diamond.
The Nature of Diamonds - The American Museum of Natural History offers this exceptional site, which includes a description of diamonds, discussion of origins and history, mining and distribution information, use in industry and technology, use in jewelry and gems, and bibliography.
Links to Groups Studying CVD Diamond - The Bristol University chemical vapor deposition diamond group maintains this list of other groups engaged in similar research.
The Chemistry of Carbon - This article provides an overview of basic chemistry associated with carbon, emphasizing the crystallographic difference between graphite and diamond.
The Nature of Diamonds - The American Museum of Natural History offers this exceptional site, which includes a description of diamonds, discussion of origins and history, mining and distribution information, use in industry and technology, use in jewelry and gems, and bibliography.
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GIA Institutes New Grading Policy for HPHT and Irradiated Diamonds
The Gemological Institute of America's Gem Trade Labs have instituted a new grading policy for high pressure/high temperature-treated diamonds and artificially irradiated diamonds. When the GTL identify such gems, the diamonds will be laser-inscribed and the lab's findings detailed on the report.
When HPHT processes or irradiation in diamonds are detected by the Gem Trade Labs, that finding will be displayed prominently on the grading report. In the color section of the report, under origin, the disclosure will state that the diamond was either "HPHT Annealed" or "Artificially Irradiated."
An asterisk next to this color section denotes further disclosure in the comments section.GIA says that before the grading report is printed, the diamonds will be laser inscribed with "HPHT Processed" or "Irradiated" and any registered name that corresponds to the diamonds will also be inscribed. GIA's unique report number corresponding to the grading report will also be laser inscribed. GIA's new grading policy was formulated as the industry sees increasing numbers of diamonds and diamond types that are subject to some form of color changes through HPHT annealing or irradiation.
While experiments with HPHT have apparently gone on for some time, the diamond market only became aware of the dramatic changes it could have on diamonds two years ago when Pegasus Overseas Ltd., a subsidiary of Lazare Kaplan International, announced its new HPHT process. It was later revealed that General Electric Co. was supplying the technology to process certain Type IIa diamonds to convert them from brownish colors to the much more marketable colorless range.
These diamonds are now sold as Bellataire™ processed diamonds. GIA, the Gübelin Lab (Lucerne, Switzerland), the SSEF Lab (Basel Switzerland), and others then embarked on projects to identify the characteristics of diamonds that had been processed by HPHT treatment."GIA has devoted a great deal of its research efforts to developing practical criteria for identifying HPHT annealing," says Tom Moses, GIA Gem Trade Labs vice president. "GIA has examined more than 3,500 GE-processed diamonds to date and has benefited from research performed by other esteemed organizations.
As a result, GIA researchers have been able to isolate several gemological and spectral features that are effective in identifying HPHT processed diamonds.""Because both HPHT annealing and artificial irradiation produce results that are stable in normal conditions of wear and care, we feel it is appropriate to issue GIA Grading Reports on diamonds that have undergone the process," adds Thomas C. Yonelunas, GIA Gem Trade Labs CEO. "The policy is in the best interests of the trade and the consumer as it both addresses the critical need for the disclosure of such processes, and provides a comprehensive analysis of the diamond's quality."
- by Robert Weldon, G.G. October 3, 2001
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Diamond Imports
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