Ollivander only makes wands with phoenix feathers, unicorn hair and dragon heartstring, even though it's possible to use different cores like Veela hair and it seems to be implied that anything string-like from any other magical animal or being could work.

... what about changing the wood? What other materials could be used in place of wood? Or could they? What would happen if you tried making a wand out of... metal? or stone? or glass? ... or shell?