Gave Dave the same info doug.
Here are the tests for Silk rugs
Tests for Silk rugs, first
OK, you're looking at a nicely woven, nicely patterned, closely clipped "silk" rug with what appears to be real silk fringe. You still might be looking at a rug made of artificial silk. Here are three field tests that might help you distinguish real from fake. No guarantee; your mileage may vary.
Rub it! It is sometimes claimed that you can tell real silk from artificial silk by vigorously rubbing the pile with your open palm. The real silk rug feels warm, the artificial silk rug stays cool to the touch. We sometimes think we have felt this difference. Of course, it helps to have a real silk rug with you so that you can compare a known quantity!
Burn it! This test is at least good theatre, and actually can be helpful. Clip off a small piece of the fringe, or pull a knot out of the rug from the back (why should the owner object?). Burn it. Look at the ash and smell the smoke. If the material was cellulose (rayon), the ash should be soft and chalky, and the smell should be like burning paper (most paper is made of cellulose). If the sample is real silk, the burning sample should ball to a black, crispy ash, and the smell should be of burning hair (you're burning protein, the same stuff your hair is made of). You've got to be a little careful with this test to avoid smelling the smoke from the match (and to avoid igniting yourself or the rug dealer's shop).
Chemical Test that Doug has Chems for
Dissolve it! The most accurate test is one that chemically differentiates protein from cellulose or petrochemicals. One such test: at room temperature, mix a solution of 16 g copper sulfate (CuSO4) in 150 cc of water. Add 8-10 g glycerine, then caustic soda (sodium hydroxide: NaOH) until a clear solution is obtained. This solution will dissolve a small sample of natural silk, but will leave cotton, rayon, and nylon unchanged