Recent developments in the growth of synthetic quartz

Processes for the growth of large crystals of synthetic quartz of piezo-electric quality are now well-established. They all involve the recrystallization of quartz from solution under conditions of elevated temperature and pressure. Two recent developments, which could have profound effect in the future, are described, namely the use of impure nutrients as the source of silica, and the development of a technique for the growth of crystals of the highest possible quality for use in frequency standards and other high-stability applications.