synthetic beryl, emerald, gems

As-grown and faceted crystals of synthetic hydrothermal emeralds from the USA and USSR were compared in terms of morphology, internal features, and physical properties. The USSR emeralds are notably closer to natural emeralds in physical and optical properties, although both types differ from natural stones primarily in their internal features. USA emeralds (SG: 2.67–2.68, RI: ω 1.572–1.574, ε 1.568–1.569) display bright red fluorescence under 365 nm UV, show Chelsea filter reactions (red), and often contain optical strain, “earthworm” cracks, phenacite, and 2- or 3-phase inclusions—often originating from natural beryl seed plates. USSR emeralds (SG: 2.70–2.71, RI: ω 1.583–1.586, ε 1.577–1.579) are slightly softer (H 7–7.5), show weaker UV fluorescence and pleochroism closer to natural emeralds, and lack spikes or strong zonation. Their inclusions include more naturalistic features like “wheat-head” textures, 2- and 3-phase inclusions, and reddish-brown plates. Growth habits differ slightly, with the USSR stones typically showing multiple growth planes ({112̅1} and {112̅0}) and shorter estimated growth times. Overall, USSR hydrothermal emeralds reach ~90% similarity to natural emeralds, versus ~80% for USA stones and 40–60% for flux-grown emeralds.