In the past I've spent quite a lot of time cutting stones, mostly opal. I've also made a bunch of jewelery both modern and medieval. I wouldn't call myself a jewellery yet but I do like to dabble. One of the major restrictions I've had is finding acceptable (cheap) substitutes for expensive stones for medieval replicas, i.e emeralds and rubies. I especially want emeralds for Byzantine items.
Making synthetic emeralds out of topaz/rock crystal or gypsum- I HAVE to try thing. First step - buy some beads of each to experiment with.
Research by Dr Marjolinj Bol, Ass. Pro. of Art History, University of Amsterdam.