The wool of which animal is considered the most expensive in the world?

The vicuña ("Lama vicugna") is one of the two wild South American camelids, which live in the high alpine areas of the Andes. Vicuñas are relatives of the llama, and are now believed to be the wild ancestor of domesticated alpacas, which are raised for their coats.

The wool is popular due to its warmth, and is used for apparel such as socks, sweaters, accessories, shawls, coats, and suits, and home furnishings such as blankets and throws. Its properties come from the tiny scales on the hollow, air-filled fibres. It causes them to interlock and trap insulating air. Vicuñas have some of the finest fibers in the world.

The vicuña only produces about 0.5 kg (1.1 lb) of wool a year, and gathering it requires a certain process. During the time of the Incas, vicuña wool was gathered by means of communal efforts called "chacu", in which multitudes of people herded hundreds of thousands of vicuña into previously laid funnel traps. The animals were shorn and then released; this was only done once every four years. The vicuña was believed to be the reincarnation of a beautiful young maiden who received a coat of pure gold once she consented to the advances of an old, ugly king. Because of this, it was against the law for anyone to kill a vicuña or wear its fleece, except for Inca royalty.

As of June 2007, prices for vicuña fabrics can range from US$1,800 to US$3,000 per yard. A vicuña wool scarf costs around US$1,500.