gems, beryl, emerald

An important chemical analysis of a Peruvian emerald by Nicolas-Louis Vauquelin. By comparing its composition with that of beryl, Vauquelin demonstrated that emerald and beryl are essentially the same mineral species, despite their different colors and traditional classification as separate stones. His analysis also identified the newly discovered earth glucina (beryllia, BeO) as a constituent of emerald. Vauquelin further investigated the cause of the green color and detected chromium, which he had recently discovered, attributing the emerald’s coloration to this element. The paper was therefore a major contribution to gemstone chemistry, establishing the mineralogical relationship between emerald and beryl and identifying chromium as the coloring agent of emerald.