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[Article] A Remarkably Large South Sea Pearl


A Look Inside a Remarkably Large Beaded South Sea Cultured Pearl By
the Gemological Institute of America

An exceptionally large, lustrous baroque-shaped South Sea cultured
pearl from Indonesia was studied by high-resolution X-ray computed
microtomography (X-ray =B5-CT). The undrilled specimen measured 34.6
mm wide and 40.3 mm long. It was hollow and contained a loose bead.
Analysis revealed a large internal cavity filled with liquid, gas,
and organic material. The nacre thickness averaged 2.3 mm, and the
bead measured 9.1 mm, both well within the typical ranges for South
Sea cultured pearls. It is proposed that the cavity was originally
occupied by spongy, water-bearing organic material, which inflated
the pearl sac and provided a supporting surface for nacre deposition
at a distance from the bead. After the nacre coating fully enclosed
the organic material, gases were liberated and trapped inside the

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