gems, corundum, synthetic corundum.7, Ramaura, flux, YAAG, synthetic garnet

Gübelin describes two recently introduced artificial gem materials: Ramaura flux-grown synthetic ruby and yttrium aluminium gallium garnet (YAGG), a green artificial material used as an imitation of tsavorite. For Ramaura ruby, he discusses manufacture by flux growth at about 1250°C, the use of chromium as the coloring agent, and the effects of flux constituents and growth conditions on crystal form. Because its conventional physical properties closely resemble those of natural ruby, identification relies heavily on microscopic examination; numerous characteristic inclusions are illustrated, while UV-visible spectroscopy is reported to offer no certain separation. The second material, YAGG, differs markedly from tsavorite in its physical properties, with refractive index around 1.90 and specific gravity 5.06–5.08. Gübelin describes its composition and characteristic yellowish flux inclusions and notes that, despite its garnet structure, it is not a silicate. The article contains 42 photographs and illustrations.