There is silk used for blouses which is very light weight. Dress weight silk is a heavier weave, it can be thin and flowing or firmer like the duponi silks. Your pattern for the quilt will depend largely on the type of silk you get. For the very thin and flowing silks, you can use a lightweight backing fabric for support. However, for that, use a familiar pattern. Thin silks do not withstand a lot of stress and ripping out stitches can destroy the delicate surface. I would suggest larger pieces in your pattern. Thin silk is very easy to get off grain. But it can be made into a beautiful quilt.