Originally Posted by
SeñorPyro
re: the original post - amethyst is a type of quartz. typically, quartz can be encased with various outcomes. usually amethyst, citrine and other types of colored quartz lose their color and become cloudy when being encased. some don't like how it looks, others do, just preference. i second GreyMatter mostly except I do encase garnet, magnetite and real opals. the trick with magnetite (and most other iron bearing minerals) is that you need a really low temp so as to not boil out the iron. the trick to real opals are....welll...i can't give that one away...but it can be done.
about the other post, there are hundreds of minerals that can be encased despite what many say. I devote my glassblowing career to encasement of gems, minerals and extraterrestrial rocks. PM if you want more of an idea of what works (or doesn't).
and one last note, sometimes a certain mineral from one location in the world won't work, whereas the same mineral from a different location will. try multiple samples from various locations before you declare a certain mineral won't work. you would probably be surprised how different different samples can act.