Steelsilk

Not really silk, steelsilk is the alchemically-treated fiber of the blue-thorn vine, which grows only in the Jungle of Fangs. A parasitic vine, it cannot be grown in captivity, but plantations of trees most suitable for its growth are maintained. The thorns contain a toxic chemical that makes harvesting it difficult; in addition the alchemical treatments required to make the fiber usable are both expensive and dangerous. This makes steelsilk one of the most expensive fibers in Noefra.

It's worth it, though. It has a metallic sheen even when dyed, and has the strength of fine steel but the pliability and workability of silk (hence its name). Becoming a craftsman or merchant of steelsilk requires government approval in all three nations of the jungle; a single bolt costs hundreds of gold raw. Many noble families in the Jungle only own a single garment of steelsilk, usually a blue-dyed sur ao dao worn only on the most special occasions.