I Agree Tim, Asomotif , Craftmanship is most important, but the qualities of rhino to take fine carving and stand without splitting for centurys leave buffalo , goat & cow fast behind,
Also of course its practical qualitys of grip & its historical significance in many cultures.
It becanme rare & valuable because it was great material. Not the other way round.
i guess the Chinese pharmascists must have goo tests, unless they can also just "see" it due to handling the real stuff.
I guess to some people Rhino horn is also a power motif? rather like Tiger teeth & human skulls?
But without doubt it is the soundest horn there is.