spalting
n.— «Wood left on the ground for several months, he said, will undergo “a startling transformation and develop a spidery network of black lines.” This process, called spalting, “is due to special fungi that live in the ground.”» —“Artists work in oil and wood” by Rebecca Bailey in Carrboro Herald-Sun (Durham, N.C.) Sept. 29, 2005. (source: Double-Tongued Dictionary)