Henry,
Briefly,
Ivory is translucent relative to bone.
Ivory is denser therefore heavier, relative to bone.
Ivory exhibits a pattern of fine lines ranging from parallel to crosshatched, bone does not.
Bone often exhibits a pattern of dark flecks ranging from dark brown to black, ivory never does
I could go on but this should be enough.
-StevenK
p.s.-good luck with making some new "potter friends", and hopes for a successful quest!
p.p.s. -"Schreger lines" can be extremely difficult to see on the finest grades(TOKATA) of asian elephant ivory so careful inspection is recommended.