What is a Narwhal's horn made out of?

The narwhal's horn is actually a tooth.

According to this site it is made of ivory.

http://www.swanseaheritage.net/article/gat.asp?ARTICLE_ID=614&PRIMARY_THEME_ID=2

Thanks so much :)

To take the answer a little further. Ivory is dentin. Dentin consists of the area of the tooth above the tooth pulp and under the enamel. It contains a mixture of minerals, collagen, and water. The mineralized tissue is much stronger and more durable than bone.

A Narwhal's horn is not actually a horn; it is a tusk. The tusk is a characteristic feature of male Narwhals and can grow up to 9 feet long! It is an elongated tooth that extends from the upper left jaw and spirals counterclockwise.

The Narwhal tusk is made up of dentin, which is a hard, dense material similar to the substance found in human teeth. The tusk is covered by a thin layer of enamel, which gives it its characteristic smooth appearance. Inside the tusk, there are millions of tiny tubes filled with nerve endings, giving it sensory capabilities.

As for how we know this information, it has been studied and researched by marine biologists and scientists. They have examined Narwhal tusks obtained from scientific expeditions, museum collections, and observations in the wild. Additionally, advancements in technology, such as imaging techniques and DNA analysis, have allowed scientists to gain insights into the composition and growth of the Narwhal tusk.