Silk is not an easy fabric to identify. There are numerous tests for properly identifying silk fabric but one that's easily conducted without chemicals or training is simply called the burn test. As the name implies, you need to burn the fabric (a small piece or even a thread will do) and then watch what happens. If you know what to look for, then this process should be an easy and safe way to figure out whether what you have is genuine silk.
Pull a thread from the fabric you're trying to identify. Several threads, or even a very thin swatch of the fabric, will do as well.
Hold the thread over a nonflammable surface and light it on fire. Make sure that you extinguish the match or lighter immediately afterward.
Watch the thread as it burns. If the thread is genuine silk, it won't burn but it will glow faintly. It will also give off the smell of burning hair.
Dip the thread in the bucket of water to extinguish it. Make sure that the heat is dissipated and that there's no risk of fire before you clean up.
The reaction you get when you do the burn test on silk thread is very similar to the reaction of the same test with wool yarn.
Make sure that you keep your bucket of water close by. Some fabrics that look like silk are actually extremely flammable and will need to be doused immediately.