I post this as it is a splendid picture that you can zoom in on. See how it chips like wood. I would say it is only very slightly translucent due to the thin section of the sides of the cup, the base is rather different. I believe there can be considerable colour variations. Perhaps we could examine the pieces we have and discuss why we believe them to be Rhino horn. Maybe see and learn a great deal more?
http://southernsudan.prm.ox.ac.uk/de...49.8.127_a.jpg