Amadou fungus (Fomes fomentarius)

This has been used since ancient times and was a precious resource as it was used as tinder to light fires and recorded evidence of its use as long as 5000 years ago.
It was also highly prized by my dad and other fly fishermen for its super absorption qualities. It was used to dry out artificial dry flys so they floated on top of the water. Its mostly been replaced by artificial products now.
It was also treated and beaten to form artificial leather products.