Silk

Silk is a natural fiber that is created from silk worms. It is used by both humans and Smurfs for various functions.

Empath: The Luckiest Smurf stories
Silk in the EMPATH: The Luckiest Smurf story series is collected by the Smurfs and made into fabric by Weaver to be used by Tailor for making clothes and other items made of cloth.