here is a test for fabric content.
take a small piece of fabric, 2"x 1/4" is plenty big enough. hold the fabric scrap with a pair of metal tweezers. using a lighter, or match, ignite the end of the scrap, allow it to burn a little then blow it out. if there is a gray ash that smells kind of like wood or leaves burning. it's cotton. if there is a hard bead, it is poly. and if it smells like vinegar (sort of). if it smells like burning hair it's wool or cashmere (or any fabric derived from animal hair.) if there is a combination of elements in the ash, like a soft gray ash with a beaded edge, it's poly-cotton. hope that helps. stores won't let you test in the store, but they will give you a small sample you can take outside and test. at home, of course, it's not a problem.
i wrote this before i'd read the second page. sorry to be redundant!