Gemology Hub | Gemstone & Mineral Identification Guides

  Gem-Quality Synthetic Diamonds In 1970, General Electric announced a modified growth process that enabled them to produce large synthetic diamonds by the HPHT process. This technique is known as the ‘temperature gradient method’. With this approach, the carbon source is placed near the middle of the growth capsule, and one or more synthetic diamond seeds are placed on a ‘seed pad’ at the bottom of the capsule. A substantial layer of the metal solvent-catalyst is placed between the carbon source and the seeds. The temperature of the reaction volume is raised by a graphite heater sleeve surrounding the growth capsule (this is referred to as ‘indirect heating’). The bottom of the capsule is slightly cooler than the centre, and so there is a temperature gradient between the carbon source and the seeds. When the metal is melted, carbon dissolves at the central region of the capsule and moves down towards the seeds. Because the seed region is slightly cooler, diamond crystals begin to ...

  Instruments for Assessing Gem Diamonds DTC has developed three screening instruments for examining and evaluating diamonds rapidly: DiamondSure™ DiamondView™ DiamondPLus™ The DiamondSure The DiamondSure measures the absorption spectrum of a faceted gem diamond. The majority of natural near-colourless diamonds are type Ia, and absorb strongly in the UV spectrum at wavelengths less than approximately 330 nm. Many also contain sufficient N3 centres to be detectable in a room-temperature absorption measurement. Near- colourless type IIa diamonds, on the other hand, have neither of these absorption systems present. In the case of fancy yellow diamonds, a natural cape diamond would exhibit strong N3 absorption whereas a synthetic yellow diamond has a quite different absorption spectrum. Using these, and similar criteria, the DiamondSure will specifically identify about 98% of natural diamonds and refer all synthetic diamonds for further tests. About 2% of natural diamonds will also be ...

Chemical Vapour Deposition Diamonds Researchers have found a way to grow diamond at a pressure of less than 1 atmosphere by a process of CVD (Chemical Vapour Deposition). In this procedure, a carbon-containing gas, usually methane, mixed with a large amount of hydrogen, is passed into a quartz tube and a pump maintains the pressure at about 5% of atmospheric pressure. Microwave power fed into the tube creates a plasma and also heats a substrate to approximately 800°C. The carbon is subsequently deposited on the substrate, mostly as graphite, but some carbon atoms bond together in the diamond crystal structure. The atomic hydrogen in the plasma removes graphite very readily but does not react with the diamond. The net result is that a thin film of diamond remains on the substrate. The diamond films were generally grown on substrates such as flat sheets of silicon or molybdenum and were polycrystalline. The brown colour of early films is generally attributed to non-diamond carbon at the ...

Exploring The Uniqueness Of Triple X Diamonds: What Makes This Cut So Special? The term "triple X diamond" refers to round brilliant diamonds that have been assessed Excellent cut, Excellent symmetry, and Excellent polish by the GIA. Because X stands for Excellent, Triple X simply implies Triple Excellent. The cut, symmetry, and polish grades of a diamond demonstrate the level of craftsmanship that went into turning a rough diamond into a polished stone. All three affect a diamond's light interaction and are graded Excellent, Very Good, Good, Fair, and Poor on GIA Diamond Grading Reports. Many diamond purchasers look for Triple Excellent diamonds because they desire the greatest craftsmanship possible. A diamond's top-notch craftsmanship guarantees that it emits the most light and fire while also having a pleasing pattern. What does it mean to have an excellent cut? The most significant aspect of a diamond is its cut. It influences the dimensions of a diamond, such as...

  Natural extravagant dark precious stone (6.21 ct) flanked by two rubies in a ring by Raiman Rocks. Regular shading jewels that seem dark are the aftereffect of: 1. Dark considerations (the most widely recognized sort), e.g., graphite, hematite as well as iron 2. Hydrogen-related mists all through that are so thick the stone looks dark 3. A dull earthy colored shading that is so dim, the stone looks dark 4. Normal light (Gems and Gemology, "Dark Diamond with Unusual Color Origin," Winter 2013, Lab notes). Most dark jewels are intensely broken stones that have been warmed until the cracks graphitize and become dark. These warmed precious stones are regularly utilized for globules and skirmish. Some treated precious stones that look dark have been lighted. These will generally have a dim green to blue shading that is so dim the stone seems dark. Nonetheless, in solid sent light illuminated jewels ordinarily look dim blue to dull green. When utilizing communicated light to obse...

  Synthetic Diamonds: A Brief History In the early part of the twentieth century, several attempts to synthesise diamond were conducted, and by the 1940s, the temperature and pressure parameters under which diamond is the stable phase of carbon had been established experimentally. Berman and Simon expanded on these findings. Graphite is the stable phase at normal temperatures and pressures, which is interesting. At normal temperature and standard atmospheric pressure, diamond, the ultimate gemstone, is merely meta-stable! Fortunately, converting a diamond to graphite requires a lot of energy, and in an inert atmosphere, a diamond may be safely heated to at least 1500 °C without causing harm. When the temperature rises beyond 1800 °C, however, the material quickly transforms into graphite. Following the availability of tungsten carbide in the 1930s, serious attempts to synthesise diamond started. This exceptionally strong material enabled the development of pressure cells capable of...

حیرت انگیز ڈائمنڈ ٹوئن دو ہیرے کے کرسٹل جو جڑواں میکل ہیں اور نایاب ہیروں  غور  کرتے  ہیں۔ دو فلیٹ مثلثی کرسٹل (جسے میکلز کہتے ہیں) ایک ستارے کی شکل بنانے  کے لیے بالکل صحیح زاویہ پر اکٹھے بڑھے۔ بائیں جانب جڑواں ہیرے کے کرسٹل کا وزن 0.92 کیرٹ اور دائیں جانب والے کا وزن 0.97 کیرٹ ہے۔ Rare Twinned Diamonds  تصویر: رابرٹ ویلڈن/جی آئی اے۔ بشکریہ: مارون فنکر، ٹریلین ڈائمنڈز۔ Related articles Minerals / Gemstones crystal Systems Diamond Genisis and Chemical composition Optical properties of Diamond

  Detecting   Treated,   Synthetic,   Colour- Enhanced   and   CVD   Diamond At the present time large numbers of natural diamonds are treated, using   radiation, on its own, or followed by heating at approximately 800 °C to   produce green, yellow and orange diamonds, and possibly a few pink   stones. Small quantities of HPHT synthetic diamonds are appearing in   the diamond trade; most of these are fancy yellow and some are irra-   diated and annealed to generate fancy pink colours. Colourless and blue   HPHT synthetic diamonds are more difficult to manufacture, and are   seen in only very small numbers. Significant numbers of natural brown   diamonds are being colour-enhanced to produce near-colourless stones,   from type IIa starting material, and fancy yellow and fancy yellow/green   colours,   from   type   Ia   starting   material.   Because   fancy   colou...