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Showing posts with the label Synthetic Gemstones

Gemstone Windows and Dark Patches: What to Look for in a Cut Gem

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AI-generated educational illustration. Conceptual only; not a photograph of an actual specimen or location. A coloured gem may have a pale, see-through centre or areas that look almost black. Both affect its appearance, but they do not have the same cause. What is a window? A window is an area where light passes through the gem instead of being returned towards the viewer. You may see the background through it, especially near the centre. Cutting angles and the material's refractive index—how it bends light—help determine whether this happens. There is no single ideal depth for every gemstone. Why dark patches need a closer look Darkness can have several causes. The material may absorb a lot of light. Some facets may reflect dark surroundings or the observer. Extinction is another cause, involving light that is not returned to the viewer after internal reflection. For that reason, calling every black patch “extinction” can be misleading. A simple viewing routine Look at the gem fac...
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Flux-Grown Synthetic Red Spinel: Why Basic Tests Can Be Misleading

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A synthetic spinel is grown by people but has the identity of spinel. It is different from a material that only imitates spinel’s appearance. Flux-grown red spinel is a useful example of why a correct mineral identification does not always establish natural origin. Why routine measurements may overlap SSEF’s 2009 study reported flux-grown red spinels with refractive index and density similar to natural spinel. Their attractive appearance and fluorescence were also insufficient for reliable separation. A familiar result on a basic gem test therefore did not settle the formation question. What the researchers examined Microscopy revealed cavities containing flux residues, sometimes with gas bubbles, and a metallic flake in one specimen. Chemical and spectroscopic observations helped support the interpretation. Brown material inside a fissure must not automatically be labelled flux. Natural spinel can contain other brownish substances, and a similar-looking feature may have a diffe...
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