Imitation rubies are most commonly found antique jewelry in the form of ruby doublets and triplets, which are composite stones. Composite stones are jewelry pieces comprised of more than one stone bonded together.

Ruby doublets
Ruby doublets were first used in antique jewelry. There are two types of ruby doublets - the true doublet and the false doublet.

True ruby doublets are created using two genuine rubies and then bonding them together to form a single, larger ruby of better color than the originals. For example, using two pale yellow rubies with a deep red glue will create a larger, intense red composite stone.

False ruby doublets consist of a thin slab of ruby that is glued on top of a colored glass bottom to form a large composite ruby.