Meh, given that so far we've seen not a single bit of stone on the KO & they're a race living in the skies, that does seems rather odd. Does the symbol that's on it resemble anything?
Course they do Could be a device for one of their diviners/wizards/engineers. Imho the way it looks it looks a bit like something for divination which is why I'm not sold on it being KO. THough the picture @Aginor linked also has a KO with a chunk of rock for no reason, so I guess they carry around rocks for fun. So I guess it works. In all seriousness, why does that KO have a random rock mounted on him?