You're welcome, I'm glad I could help.
In guide Carl listed all gems with expansions they come with. And in skill journal you can get info about requirement for "special cut". In total there is 25 gems and 12 available cuts, but getting other gems into spire and split polished half's is possible only through transfiguration, as well as getin skull cut for any gem. I also never saw tiberium in any other shape but spire, heart and skull, even if theoretically it should be possible to get emerald cut tiberium as it is for geode and septarian nodule (which I already have). Easiest way to get this challenge done is to have martial artist who is spawning gems by breaking space rocks.