Many dealers do not know the difference between ivory and bone and therefore mistakenly list bone or resin items as "ivory".  Bone has dots and dashes instead of the cross-hatching or wood-like grains of genuine elephant or mammoth ivory.  Hippo ivory has a glossy texture and usually has a dentine line showing in the carving. Resin will have a pour mark, bubbles from the pour, or seam marks in most pieces.  If in doubt, take the item to someone dealing in genuine ivory, not your local antique store.  Mammoth ivory is legal to ship anywhere in the world without permits.  Hippo, pre-CITES elephant, whale, norwhal and some other types of ivory require a CITES permit, but you should also check with your local customs office since some countries restrict the import or export of certain types of ivory.