Build multiple green, translucent gem pieces with exacting shapes.
In order to create multiple parts that will all come out the same, the best method is to build a mold first. In this case, I'm making one out of something called RTV urethane. First I have my solid objects that I intend to copy. They need to be completely sealed (using shellac and wax) and then firmly stuck to the bottom of a smooth, makeshift container (I used double-sided tape for the wooden dome piece but used hot glue for the bigger shape).
Thoroughly mix the RTV with the catalyzer and pour into the container (it's just like baking a cake). Until it finally solidifies, urethane is very gooey and can cause your object to float up to the top, thus ruining your mold, so make sure the object is firmly secure to the bottom.
When the urethane hardens, you can freely tear apart the container and dig out the wooden piece inside (provided it was sealed with enough wax). Urethane is amazingly good at boding ONLY with itself so everything else will peel right off. The mold is also very rubbery so you can wriggle and pry your piece out of there without breaking anything.
Using these two molds, I can make duplicates out of them using any sort of material, in this case, I'm using polyester resin (this is the same chemical used to make fiberglass). Again, the resin needs to be throughly mixed with its own catalyzer and then, in the case of this project, some green dye is added in with the mixture before finally pouring that into the urethane molds. The resin will turn rock hard eventually, but heating it up will speed the process up- so will adding more catalyzer, but that can be dangerous because you have less time to work with.
Anyway, the resin will easily peel off the urethane, and the whole process in Panel 4 can be repeated over and over again until you have what you need.