Here's some places to get great fabric online. If the fabric contains polyesters or similar synthetic fibers in it the burned edge will have small hard plastic globules, where the plastic melted instead of burning. If the fabric is pure cotton, nothing will remain but a gray ash that easily disintegrates. If the fabric is pure silk, the fabric will be hard to ignite and will give out a distinctive oder. I don't know for sure what wool does, but I think it gives out the odor of burned hair.
Rayon burns much as cotton does, as it is celluose and is hard to tell from cotton with a burn test.