synthetic beryl, emerald, natural beryl, emerald, gems

Electron-microprobe analysis is investigated as an additional means of distinguishing natural from synthetic emerald when conventional gemmological properties and internal features are inconclusive. Refractive indices, birefringence, specific gravity and fluorescence can overlap, while inclusions and growth structures may be absent or difficult to interpret. The study therefore examines differences in minor-element chemistry, contrasting the relatively near-ideal beryl composition of many synthetic emeralds with the greater chemical substitution commonly found in natural material. Forty-five faceted stones from different natural sources and synthetic manufacturers were examined, with four point analyses performed on each specimen. Magnesium and sodium provide the clearest separation within the investigated population. Natural emeralds contained at least approximately 0.8 wt% MgO, with most values between 1.5 and 3.0 wt%, whereas synthetic specimens commonly contained around 0.1 wt% and reached approximately 0.4 wt%. Natural stones contained at least 0.4 wt% Na₂O, while most synthetic stones had no measurable sodium; the highest reported synthetic value was 0.2 wt% in a Lechleitner sandwich product. Chromium and iron concentrations overlap between the groups and consequently do not provide a general diagnostic separation. Compositional variations among natural emeralds also show patterns associated with different geographic sources, with Colombian specimens tending to contain fewer impurities than most other natural samples. A Brazilian stone labelled as emerald from Conquista contained vanadium and iron but no detectable chromium, illustrating the variability of the colouring constituents. Additional observations include 0.3–0.4 wt% chlorine in Linde hydrothermal synthetic emeralds and exceptionally high chromium concentrations in Lechleitner synthetic emerald overgrowths. The author relates the characteristic network of fissures in these coatings to lattice-dimensional differences caused by chromium substituting for aluminium. Electron-microprobe analysis is presented as a means of obtaining diagnostic chemical information from cut stones without destructive sampling. However, the author explicitly recognizes that 45 stones cannot represent the full compositional range of either natural or synthetic emerald. The magnesium–sodium distinction is therefore proposed as a useful supplementary criterion requiring broader testing, including examination of new synthetic products. Water content and additional trace elements are identified as potentially valuable future discriminants.