Growth of Emerald Crystals by the Flux Evaporation Method in MoO₃-B₂O₃ System

Abstract

The growth of emerald crystals by the flux evaporation method in the system MoO₃-B₂O₃ is reported. The crystal growth was conducted by heating a mixture of a solute (3BeO⋅Al₂O₃⋅6SiO₂+1wt% Cr₂O₃) and a flux (MoO₃-B₂O₃) at 1100°C, followed by holding at 1100°C for 10, 20, 25 and 30h. The evaporation loss of flux decreased gradually with increasing amount of B₂O₃ added to MoO₃ and increased with the holding time. The transparent emerald crystals were grown with the typical emerald-green color in size up to 1mm. The crystal size was dependent on the evaporation loss of flux. Hexagonal thin plate-like crystals were grown from an MoO₃-rich flux containing 0.15-0.60wt% B₂O₃. The plate-like crystals were bounded by the {0001} and {1010} faces. In rare cases, the small {1120} faces appeared. Crystals grown from the MoO₃ flux were twelve-sided prism in shape. Molybdenum trioxide containing a small amount of B₂O₃ was found to be a suitable flux for growing plate-like crystals of emerald.