Get yourself a fabric store that will light your fabric on fire for you

Ok but this is actually one of the easiest ways to tell what something is made of! I did a textiles degree and one day as part of a class we all went outside with a pile of scrap fabric and set fire to the little pieces and recorded how they burned. We were given a chart that looked something like this to tell what each fabric was (it gets a little tricky is it's a mix of fabrics though). Why did we do this? There is very little regulation in the textiles industry so a lot of materials are mislabelled as something they aren't and sold for more than they should be, also sometimes people buy fabric second hand or discounted which doesn't have any label at all. If you have a fabric you are having doubts about, cut a tiny piece off and do the burn test and you should know pretty fast what you are dealing with. Anyways your fabric store should be lighting things on fire because this means that they are actually checking what the fabrics are and aren't trying to pass cheap stuff off as more expensive than it is.