corundum, synthetic corundum.7, gems

Kuhlmann applies emission spectrographic analysis to 207 natural and 61 synthetic rubies, sapphires, emeralds and alexandrites, examining eleven trace elements: Be, Cr, Cu, Fe, Mn, Mo, Ni, Si, Sn, Ti and V. The analyses reveal characteristic trace-element patterns that can help distinguish natural gemstones of different geographic origins from synthetic products. Natural rubies from Kenya, Tanzania, Afghanistan, India, Burma and Greenland contain varying combinations of Cr, Si, Ti, V, Mn, Fe, Sn and Cu, whereas Chatham and Verneuil synthetic rubies show molybdenum, and Kashan and Knischka synthetics contain comparatively more copper. Natural sapphires from several localities likewise show trace-element assemblages differing from Verneuil and Chatham synthetics. Corresponding comparisons are made for natural and synthetic emerald and alexandrite. Kuhlmann concludes that emission spectrography provides a useful supplementary method for determining natural versus synthetic origin and, in some cases, characterizing geographic provenance. The paper contains eight figures and one table.