A study of emerald synthesis

Abstract

At this time there are only two known commercial synthesisers of gem quality emerald in the world. Carrol Chatham of the United States and Pierre Gilson of France. This study looks primarily at the historical research in the field of emerald synthesis with a view to developing another successful commercial synthesis. It covers important published work in the two major areas of synthesis, fluxed-melt synthesis and hydrothermal synthesis. A third possibility, that of vapour-reaction synthesis is also discussed. In attempting to ascertain the actual method used by Chatham a sample of his emerald is chemically analysed and the inclusions contained are examined by electron-probe and also tested for their thermal behaviour. Historical research indicates that the most successful fluxed melt syntheses involve the use of lithium-molybdate flux. The thermal analysis of inclusions and chemical analysis of Chatham emerald indicated that lithium-molybdate flux was used in its manufacture, however, this was not confirmed by the stronger evidence of the electron probe analysis, which did not show any element concentrated in the flux inclusions. A series of slow cooling experiments attempts to find a suitable flux for emerald synthesis which does not necessitate the use of inert-metal containers made of platinum or gold. Finally several attempts are made to synthesise emerald using vapour-reaction methods. Generally A1F3, BeF2 and Na3A1F6 are reacted together at various temperatures, and while silliminite and chrysoberyl were synthesised, all attempts to synthesise beryl were unsuccessful.