Growth of emerald crystals by evaporation of a K2O–MoO3 flux

Abstract

The growth of emerald (Be₃Al₂Si₆O₁₈:Cr) crystals by the flux evaporation method in the system K₂O–MoO₃ is reported. The crystal growth was conducted by heating a mixture of solute and flux at 1100 °C, followed by holding at this temperature for 1–10 days. Emerald crystals of lengths up to 4.5 mm and widths of 2.9 mm were readily grown isothermally. The crystal sizes were dependent on the evaporation loss of the flux and scaling up the mass of the solution. The obtained crystals were transparent and exhibited the typical emerald-green colour. The form of the emerald crystals was a twelve-sided prism bounded by well developed faces. The aspect ratios were in the region of 1.2 to 2.3. The density was 2.66 ± 0.02 g cm^–3. The IR absorption bands were in good agreement with literature data. The chromium was preferentially incorporated in the centre part of the crystals.