Marius, have a look to this thread:
http://www.vikingsword.com/vb/showth...light=thailand
Horn (water buffalo) can show a very fibrous structur when old and weathered, I think you see the same at your sewars but I am nearly sure that it's horn, like said, it would be the first I've seen with rhino horn! Belive me, it's
not a common material by sewars!
Regards,
Detlef