A triangular modified brilliant was submitted to GIA’s Carlsbad laboratory by L. Allen Brown (All That Glitters, Methuen, Massachusetts) for scientific examination. The 15.54 ct stone (figure 1, left) was presented as a Moroccan amethyst. Standard gemological testing established the following properties: RI—1.544−1.553; birefringence—0.009; optic sign—uniaxial positive; pleochroism—moderate purplish blue to purple; SG—2.65; fluorescence reaction—inert to long- and short-wave UV radiation. All of these properties were consistent with amethyst. What made this example notable was a strikingly large primary fluid inclusion under the table facet, which is easily seen with the unaided eye and confirms the natural origin of this stone (figure 1, right). The gas bubble in the fluid inclusion moves freely when the stone is turned slightly. No magnification is needed to reveal the beauty of this interactive inclusion, which can be easily enjoyed by rocking and tilting the stone
News Source : gia.edu
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