People consider ivory valuable because it can be used for multiple purposes, has a durable quality and aesthetic appeal and comes from the tusks and teeth of animals, typically elephants. Many laws prohibit poachers from killing these animals for their ivory, although the practice is still a problem throughout the world.
Throughout history ivory has been used to make multiple appliances, like billiard balls, piano keys, buttons, combs, buckles and dominoes, according to Rebecca J. Rosen's article on the Atlantic's website. Ivory is not only considered aesthetically pleasing, it has a durable quality, yet can be easily carved into, and it hardly ever splinters.
Ivory, like diamonds, also has a social significance. Elephants and other animals are killed for their ivory, a practice that is endangering many species of wildlife. As laws and regulations try to stop poachers from hunting these animals, this only seems to make ivory less common and, therefore, increase in its rarity and value.