synthetic corundum.7, gems

L.B. Benson reassesses the identification of reconstructed ruby, showing that many stones assigned to this category are synthetic corundum whose unusual features reflect growth conditions rather than the fusion of natural ruby fragments. He distinguishes reconstruction, defined as sintering natural fragments together under intense heat with or without pressure, from complete melting and subsequent crystal growth. A genuinely reconstructed stone should retain evidence of its fragmentary origin, potentially including natural inclusions, discontinuities in crystallographic orientation, and variations in hardness associated with bonding material. Benson questions historical accounts of substantial commercial production because securely documented specimens are scarce and early manufacturing methods remain uncertain. He suggests that some nineteenth-century “Geneva rubies” may have been early synthetic crystals rather than reconstructed aggregates. Intersecting curved striae, often cited as evidence of reconstruction, do not necessarily indicate separately oriented fragments. They can develop within a single crystal when the direction of deposition changes or growth is interrupted and resumed. The principal laboratory examples are heavily included rubies averaging approximately half to three-quarters of a carat, with abundant gas cavities and conspicuous intersecting curved striae. Investigation traced these stones to the bottom tips of synthetic boules, particularly those grown around oriented colorless rod seeds. Differences between growth structures in the seed and surrounding material explain the intersecting patterns, while color contrasts can produce patchy appearances. Concentrated elongated bubbles commonly extend perpendicular to growth lines and may spread outward in a fan from the rod, providing evidence of growth by progressive deposition. Benson reports that boule tips, commonly assumed to be waste, were being sold to overseas cutters, sometimes for more than flawless synthetic material, and apparently returned to the trade as cut stones potentially represented as natural ruby. Their visible imperfections could help them escape notice among natural stones. A second group consists of small, rounded, button-shaped boules long invoiced as reconstructed rubies. Cross-sections reveal orderly accumulated curved striae, gas bubbles, and synthetic seed material, supporting identification as early synthetic boules. Benson allows that cooling molten natural ruby could produce irregular swirls, but argues that this would not explain elongated gas bubbles consistently perpendicular to those lines. He concludes that most material identified as reconstructed in the trade is probably synthetic, while acknowledging reported examples retaining intact natural ruby. To reduce confusion, he recommends restricting “reconstructed” to stones consisting of sintered natural fragments that preserve characteristics indicative of natural origin.