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Star-Shaped Inclusions Spotted in Diamonds
GIA recently examined two asteriated diamonds, weighing about 8 carats each, that it said were notable for their large size and preserved natural forms.
The asteriated diamonds displayed light brown cloud inclusions shaped like stars.
Carlsbad, Calif.—Two natural diamonds with star-shaped inclusions were recently submitted to the Gemological Institute of America’s Carlsbad laboratory for examination.
The asteriated or “star” diamonds, weighing 8.14 carats and 8.57 carats, appeared in the lab’s summer 2024 edition of “Gems & Gemology.”
The stones displayed light brown cloud inclusions, which come from high concentrations of hydrogen and nickel during their growth period, said GIA, and may also contain graphite.
GIA said asteriated diamonds are occasionally submitted to the lab, but these two stones are notable for their large size and preserved natural forms.
The 8.14-carat diamond was resorbed—partially dissolved by natural fluid or magma, causing it to take on a rounded shape—and maintained most of its rough form on one side.
The stone was sliced to show the underlying inclusion pattern on the other side.
The preserved rough surfaces also displayed brown radiation stains, which are an indication that it had natural alpha irradiation followed by annealing in the earth.
The 8.57-carat diamond was polished with bruted edges.
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The asteriated or “star” diamonds, weighing 8.14 carats and 8.57 carats, appeared in the lab’s summer 2024 edition of “Gems & Gemology.”
The stones displayed light brown cloud inclusions, which come from high concentrations of hydrogen and nickel during their growth period, said GIA, and may also contain graphite.
GIA said asteriated diamonds are occasionally submitted to the lab, but these two stones are notable for their large size and preserved natural forms.
The 8.14-carat diamond was resorbed—partially dissolved by natural fluid or magma, causing it to take on a rounded shape—and maintained most of its rough form on one side.
The stone was sliced to show the underlying inclusion pattern on the other side.
The preserved rough surfaces also displayed brown radiation stains, which are an indication that it had natural alpha irradiation followed by annealing in the earth.
The 8.57-carat diamond was polished with bruted edges.
Both diamonds’ clouds fluoresced green when subjected to long-wave UV, which GIA said is consistent with previously studied asteriated diamonds.
Also, both stones showed high concentrations of hydrogen, which the lab detected using bulk Fourier-transform infrared spectroscopy.
Using photoluminescence mapping for the 8.14-carat stone, the lab saw that several nickel-related defects were detected inside the cloud inclusion sector but not outside of it.
GIA also analyzed the diamonds using X-ray computed microtomography, which allowed the asteriated growth sectors to be viewed in 3-D reconstructions.
It found the asteriated regions more strongly absorb X-rays than the rest of the diamond.
This indicates, the lab said, the combined signal from the diamond and inclusions likely had a higher atomic number.
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