What is a rhino's horn made out of?

Rhino horns are composed of a fibrous protein called keratin, which is the same substance found in human fingernails and hair. Keratin is also present in feathers, claws and hoofs.

A rhino's horn is not attached to its head but is a compacted mass of hair that continues to grow throughout its lifetime. The center of the horn contains two mineral deposits which explains the curve and sharp tip. Calcium strengthens the horn, and melanin protects the core from ultraviolet sun radiation. Keratin composition depends on the animal's diet and geographical location. Horn samples are similar to human fingerprints. Law enforcement officials use these samples to locate illegal areas of poaching.