My wiki-fu has reminded me that
cabochons are gemstones cut into a round, often elliptical, shape. It appears it's common to do this with some more ordinary types of stone too, which would be a nice way for normal stone to join the extensive list of gemstones, if that is the intention. If I understand that right, it would also mean normal stone could be converted into a gem, which would be encrustable into an object made of normal stone, compressing those inevitable heaps of worthless mountain pieces into beautiful trade goods that much faster and with more detail.
I wonder if dynamically generated fossils would be a good suggestion for a future release... They'd certainly be wonderful for making into gemstones. "This is a polished bee fossil. The fossil is of a bee and a leaf. The bee is sitting on the leaf." ... "This is an ancient fossil. The fossil is of a tiny lizard twisted into humanoid form with exposed ribs and feathers. The lizard is curled inside the faint outline of an egg shell." For bonus points, it could also mention what type of stone it is in... or perhaps that's going too far?
Also of note is
cameo and
intaglio carving of gemstones (perhaps using cabochon-cut gems and stones as a material?) into images like wall engravings, which would be awesome too.
Ostrich gizzard stone gems... heh! I like where this is headed.