User blog comment:BobTheDoctor27/February 2013 Update/@comment-5072107-20130312204042/@comment-958607-20130313074723

There's nothing special about a Toa Stone itself. Usually they are just rocks that a Toa find and decide are pretty enough to serve as a vessel to contain his/her Toa Power. Theoretically, anything could be a Toa Stone, which is why I made the Vahi one. At some point in history, a Toa planted his/her power into the Kanohi so that, when a Matoran put it on (or it made contact with Danza's Kanohi by accident when he was turning it over in his hands) they would transform into a Toa. I guess I just kinda answered my own question. XD I'd forgotten that no other Matoran would have put the mask on their face. :P