silkfabric.org

BURN FABRIC TEST WARNING , ALL FABRICS WILL BURN! Burn fabric test must be in a safety environment to avoid accident , and must have a metal bucket of water and have Fire extinguisher handy in case the fabric burning. If you doing the burn test it at your own risk, we do not encourage anyone to burn any fabric.
We just sharing our experience here.

To test fabric if its silk, burn test can tell you if the fabric is silk or not, we do use this test when we buying materials from wholesale market / supplier shop. And may use this test to check the wool/cashmere as well.
Silk is protein they burn very quickly, for example if its silk charmeuse {100 % Silk} you may cut a small piece of the fabric and put it in an ashtray then burn it with a lighter / match, it will be smells like burning human hair when it burning, if you smash the ash gently it will be all crumbled -same as cigarette ash- but in much smaller / finer form. The more fine crumbs from the ash it has more silk contents.
If the fabric passed this burn test, then it should be real silk – though you may still need some experience for fabric, and its better to buy silk fabrics from trustworthy shop or online store.
Link to Our online silk charmeuse shop