Glossary
Foilbacks
Practice dating back to the 12th century, in which gemstones were enhanced in colour and lustre by inserting a shiny (coloured) foil made of copper, silver or gold into the setting of the respective gemstone or gluing it to its underside. Gemstones in the late Middle Ages and early modern period were almost always foil-backed. Foilbacks only disappeared completely in the 19th century.