Sorry if this is a silly question, but I happened to notice that while there are instruments made out of wood and/or metal and even plastic or glass, there are no rock-based instruments. It seems that since rock is so abundant, at least a few instruments over time would have been based off of it.
Possible reasons for the lack of rock-based instruments:
- It would be too heavy (but then again I don't see people holding grand pianos)
- It is too hard to shape (but then think of ancient temples made of stone; plus we have power tools which would make the task significantly easier)
- Rock-based instruments simply don't sound good. I don't know much about acoustics, but I doubt this, especially since rock could lend itself to an echoing unique-sounding instrument, if in the correct shape.