Hydrothermal Growth of Amethyst and Citrine in NaCl and KCl Solutions

Abstract

Natural quartz grows from solutions containing mainly Na⁺, K⁺ and Cl⁻ ions. In this experiment, the growth of synthetic quartz under the same growth conditions as those of natural quartz was attempted using NaCl and KCl solutions as a growth solution. As a result, colored quartz equivalent in quality and color tone to natural amethyst and citrine was obtained. The quartz grown from r-cut and R-cut plate seeds with iron added to the growth solution was colorless but γ-ray irradiation produced a purplish tint. The quartz grown from X-cut plate and Y-bar seeds had a yellowish tint. Although the depth of color increased in proportion to the amount of iron, it reached close to saturation with an iron concentration of approximately 90 μg/ml solvent.