gems, treatments, assembled stones, foil backing, foilback

The Gem Trade Lab Notes section (Winter 1984, p. 228) reported on emerald imitations made from colorless rock crystal quartz backed with green foil—a technique still commonly used today, even in enameled jewelry. Similarly, colorless beryl or corundum is often backed with red or green foil to mimic emerald or ruby, while silver foil may be applied behind colorless synthetic or natural sapphire to enhance its brilliance.