Thank you, Emmanuel, Vandoo, Spiral and Ibrahim,
I guess I have the answer. I have long suspected that some jambiya hilts assumed to be rhino were actually something else. It must be difficult to describe a hilt as camel hoof, etc. if you don't know what camel hoof looks like, and hence describe it as whatever it looks most similar too in the assessor's experience.
However, it occurs to me that Yemenis and Omanis would be familiar with camel hoof and not so easily fooled as us in the West might be; which leads me to wonder why all our leading experts, such as Robert Elgood, Robert Hales and leading auction house cataloguers, never mention it.
Ibrahim, have you come across camel hoof as a material?
Incidentally i have a jambiya with a white bone hilt, which may be camel, and small trinket boxes can be found in the UK which are often described as North African camel bone.
I will try to post some pictures later.
Regards
Richard
PS. Interesting article here
https://www.academia.edu/6441820/The..._various_parts