Introduction:
A light purplish-blue sapphire weighing 15.84 carats was submitted to the Laboratoire Franรงais de Gemmologie (LFG) for testing. This stone turned out to be a synthetic sapphire, but what made it especially interesting was the presence of Rose channels — a feature usually seen in natural sapphires.
What Are Rose Channels?
Rose channels are tiny hollow tubes inside the sapphire that always appear at the points where twin layers (called "twin lamellae") meet. These channels are positioned along the edges of certain crystal faces and form angles of about 90 degrees. Normally, these are features of natural sapphires.
Why Is This Discovery Important?
These channels and twin lines are common in natural sapphires, but very rare in synthetic ones. However, this sample — a Verneuil flame-fusion synthetic sapphire — had both features clearly visible. It challenges the assumption that Rose channels prove a gem is natural.
Other Findings from Testing:
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Under the microscope: Clouds of bubbles and twinning planes were observed, typical of synthetic gems.
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Under UV light:
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No reaction under long-wave UV.
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Strong blue glow under short-wave UV.
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X-ray fluorescence testing showed no gallium, supporting that it’s synthetic.
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DiamondView imaging revealed curved growth lines, a feature of Verneuil synthetic sapphires.
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FTIR (Infrared) spectroscopy showed no absorption in the 1500–4000 cm⁻¹ range, where Rose channels in natural stones usually show signals.
Conclusion:
Even though Rose channels and twin planes are normally signs of a natural sapphire, this case proves they can also appear in synthetic sapphires. Therefore, these features alone cannot be used to confirm whether a stone is natural.
References / Source Credit:
This article is adapted and simplified from:
Hennebois, U., Delaunay, A., Herreweghe, A., Karampelas, S., & Fritsch, E. (2022). Synthetic sapphire with Rose channels. Gems & Gemology, 58(3), p. 387.
Available at: https://hal.science/hal-04001745v1
Primary Keywords (Main focus):
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๐ Secondary Keywords (Supporting terms):
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