gems, quartz, synthetic quartz, synthetic amethyst, Japan, hydrothermal, polysynthetic twinning

Synthetic amethysts of Japanese production, which are now available in the gem trade, are characterized with respect to their diagnostic properties such as inclusions, growth structures, twinning, and infrared spectra. The gemstones frequently have feathers consisting of liquid-filled and two-phase inclusions, sharp growth zoning parallel to one rhombohedral face, as well as twin structures. This twinning, however, can be distinguished from polysynthetic lamellar twinning in natural amethysts.