The simplest, but not definitive, test is to burn a small amount. Wool will not ignite readily, but when it does burn smells like burning hair and what little ash it creates is "soft". Man-made...
it feels kinda soft
It feels warm and to some scratchy.it feels really cuddly and soft(but in sweaters itchy)
it comes from sheep
Wool comes from sheep, goats, rabbits, yaks, llamas, and alpacas.