Flux-Grown Synthetic Ruby with Hydrothermal Synthetic Seed Crystal
Under magnification, the most distinctive internal characteristic in the crown was the presence of strong irregular growth features: zigzag- or mosaic-like striated patterns (figure 1), typical of a hydrothermal synthetic. Other areas of the ruby lacking these irregular growth features contained hexagonal metallic platelets and high-relief, whitish flux inclusions (figure 2), typical of a flux-grown synthetic. Flux and hydrothermal inclusions have not been previously documented in the same specimen.
Laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) analysis revealed traces of Ca, Ti, Cr, Fe, Mo, Rh, Sn, W, and Pt. The low amount of Fe and Ti, the absence of V and Ga, and the presence of Pt were consistent with flux-grown corundum.
Both natural and flame-fusion synthetic ruby have been used as seed crystals in the flux growth of ruby (J.I. Koivula, “Induced fingerprints,” Winter 1983 G&G, pp. 220–227; Summer 1991 Lab Notes, p. 112). The seed crystals are generally removed during the cutting process but may, on rare occasions, be detected in finished specimens. Upon close microscopic examination, we noted that several of the flux-filled healed fractures (wispy veils) extended into the areas showing hydrothermal graining. These observations led us to conclude that the hydrothermal material was a seed crystal and that the flux healing was a secondary process to the hydrothermal growth. There was an irregular separation between the materials under brightfield illumination.
This unusual combination of a hydrothermal ruby seed with flux ruby overgrowth is the first of its kind examined by GIA.