Exceptionally Large and Well-Saturated Orange Sapphire
The Carlsbad laboratory recently received an exceptionally large orange cushion mixed-cut sapphire weighing 31.06 ct (see above) submitted for an identification and origin report. Standard gemological testing gave a refractive index of 1.769–1.762 and a hydrostatic specific gravity of 3.98, indicating corundum. This sapphire exhibits a saturated orange color that is attributed to the trace element magnesium in the stone’s crystalline structure. Microscopic examination showed altered crystals with healing and irregular bands of particles. These altered inclusions suggest that the stone underwent heat treatment. Internal characteristics similar to these are often found in sapphires from deposits of metamorphic sources. Laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) confirmed the stone had a lower content of trace element iron. The chemistry and internal features of this gemstone indicate an origin of Sri Lanka.
Rough material that will cut large, high-quality sapphires is rare, with most finished stones being less than five carats. Fine gem-quality examples of more than ten carats are considered very rare. The combination of a large size and a well-saturated orange color makes this 31.06 ct sapphire a notable gemstone.
