What is the visible ivory part of an elephants tusks made of?

Typically in mammals tusks are merely enlarged canine teeth, but in elephants they are a bit different; they are actually elongated incisors and are essentially no different from their other teeth. One third of the elephant’s tusk is hidden from view, where it is embedded deep in the elephant’s head. This deeper part of the tusk is a pulp cavity made up of tissue, blood and nerves. Like humans, the visible, ivory part of the tusk is made of dentine with an outer layer of enamel.

An elephant's tusks never stop growing. Some of the older bulls display enormous examples of this. However, the average size of tusks has decreased over the past century due to elephants being hunted for their ivory. This has resulted in the ‘big tusk gene’ becoming increasingly rare.