silicification

/ˌsɪlɪsɪfɪˈkeɪʃən/
noun
  1. The process of becoming or being turned into silica or a siliceous substance, especially in geology or paleontology.
    • Over millions of years, silicification turned the wood into a hard, stone-like material.
    • The silicification of the ancient tree trunks preserved their cellular structure perfectly.
    • Geologists study silicification to understand how fossils form in volcanic ash.