When you want to check the purity of Banarasi silk sarees, always look at the reverse side. It should have the warp and weft grids floating. Besides, the real Banarasi silk saree usually has the golden and silver zari threads which is why they are usually expensive. They have extraordinary motives like Amru, Domak and Ambi. More importantly, the authentic Banarasi silk sarees have the eight inch long patch of solid silk on the pallu. It usually goes over the shoulder. And when you buy them online, check out customer reviews and comments. It will help you get a pure saree.