Journal of The Gemmological Society of Japan

Observations are done on 10 pieces of synthetic emeralds by Scanning CathodoLuminescence (SCL) method. Specimens are identified by ordinary gemmologicaltesting together with NIR spectrum. They are grouped into the flux-grown synthetic emeralds and the synthetic emeralds by hydrothermal method. Flux-grown emeralds show straight parallel growthbands or "aurora-like" growth bands. Whereas hydrothemrmally-grown emeralds shows CL-image in which "comet-like" luminaries arranged in one direction or shows unique rhombic pattern. So, natural and synthetic emerald can be distinguished by SCL method, moreover for synthetic one, growth method can be identified.

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The growth of emerald crystals by cooling in the PbO・V_2O_5 high-temperature solutions is reported. The crystal growth was conducted by heating mixtures at 1200℃ for 10h, followed by cooling to 600℃ at a rate of 5,10,20,40,120 or 240℃/h. The grown emerald crystals exhibited the typical emerald-green color, and were up to 2.2mm in size and transparent. Their form was a regular hexagonal rod bounded by the well-developed faces. The average size of grown emerald crystals was 1.1mm when the cooling rate was 5℃/h. The crystal sizes decreased as the cooling rate increased. Emerald crystals averaging 0.5mm in size were grown when the cooling rate was 240℃/h. The most suitable cooling rate for the growth of emerald crystals from PbO・V_2O_5 flux was 5℃/h. In addition, attempts to grow emerald crystals from the high-temperature solutions weighing 0.04-0.05g were successful. The small platinum crucible (5mmφ×2.5mm) was used. The mixtures were heated at 1200℃ for 10min, followed by cooling at a rate of 600℃/h. Hexagonal rod crystals of emerald up to 0.4mm in size were grown. The time taken to obtain emerald crystals was about ten hours.

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This paper describes recent Russian colored gemstones on the Japanese market. Ruby, alexandrite, demantoid, topaz, emerald, aquamarine, tourmaline, diopside and jadeite, are mentioned. Crystallochemical properties of these gems are studied by electron dispersive spectroscopy and Fourier Transform Infrared absorption spectroscopy.

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Recently the round brilliant cut diamond which shows a heart and arrow shaped patteren observed on a certain illuminating condition has got into the news in Japanese market. Such a stone has sometimes been regarded as an excellent cut. Studies on the reasons and conditions of the appearance of this patteren revealed that (1) this patteren can be seen when a stone is illuminated in an inclination of 9 to 15 degree to the axis of brilliant, and (2) this patteren is mainly due to the arrangements of pavillion side facet of brilliant, i.e. pavillion facet and bottom brilliant facet, and scarcely to the crown facets, and (3) therefore a stone showing this patteren cannot automatically be regarded as an excellent cut brilliant. The appearance of this pattern is a necessary condition but not a sufficent one for excellent cut brilliant cut diamond.

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