Photo: Robert Weldon/GIA, Sir Oppenheimer Student Collection | Indented triangular surface features, called trigons, are visible on these natural diamond crystals Trigons are etch marks that can form if a diamond is partially dissolved in the mantle or during transport to Earth's surface in kimberlite magma.
Trigons on a diamond are a good indicator that a diamond is natural, because laboratory-grown diamonds almost never have triangular pits like these. Of course, someone could try to carve trigons into the surface of a synthetic or simulant in an attempt to pass it off as a natural diamond. Want to learn more about diamond dissolution? | Photo: Juan Zanahuria & Kevin Schumacher & other GIA staff | Beautiful "Defects" in Orange and Yellow Diamonds | Natural yellow gem diamonds are the most common of the fancy-color diamonds, while orange diamonds are among the rarest. Both owe their color to atomic-level lattice defects associated with nitrogen impurities in the diamond structure. Four major groups of defects are responsible for the color in nearly all yellow and orange diamonds. Each group shows a slightly different range in hues as seen here. These color mechanisms include: cape defects (first row), isolated nitrogen defects (second row), the 480 nm visible absorption band (third row), and H3 defects (fourth row).
Many natural, nitrogen-bearing diamonds start out with yellow to orange color. However, with time at high temperatures deep in the earth, the nitrogen atoms in most diamonds aggregate, resulting in either near-colorless stones or yellow diamonds colored by cape defects. That is why orange diamonds are some of the rarest while yellow diamonds are common enough to be seen in many jewelry stores. Want to learn more? | In the last decade, GIA's field gemologists collected hundreds of samples of blue sapphire while visiting different deposits in Mogok, Myanmar (formerly known as Burma), a region that is notoriously difficult for foreigners to access. The best Mogok sapphires have a saturated, rich, intense blue color, sometimes with a light violet component, but their colors can vary widely, from pale icy blue and delicate periwinkle to dark navy blue. Fine star sapphires have also reportedly been found in the western area, near Kin.
GIA scientists discovered that while the color intensity of Mogok sapphires vary widely, their inclusion scenes are fairly consistent and can be used to characterize these sapphires when determining origin. Burmese sapphires are famed for their extraordinarily large sizes and are second only to Kashmir sapphires in fame and desirability. Want to explore more? | We hope our gem knowledge inspires you to rock on. #knowledgerocks | |
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