The material that an elephant's tusks are made from. It is made of dentine, like our own teeth. Dentine contains calcium phosphate like bone, but unlike bone it has no living material and it has a more dense structure. The dentine is laid down in layers; these can not be seen in fresh ivory but can separate like onion rings during decay.

Though ivory is specifically elephant tusk other similar materials are sometimes also referred to as ivory, eg walrus tusk and hippopotamus teeth.