Stonesilk

If fluxsilk cloth is dissolved in strong acids and then left to precipitate, the result is stonesilk, which becomes harder the more force is applied to it, before returning to its natural state when the force abates.

Stonesilk is a light brown color, although impurities in the manufacturing usually gives it splotches of blacks and greens. It can be wrapped around something soft but will not yield if impacted with force. A robe made from stonesilk is as impervious to weapons as chainmail.

The process to make and work stonesilk is expensive, time-consuming, and lossy. It also can't produce thread, only sheets of cloth. Whoever comes up with a better process is sure to make a boatload of gold.