lignitize
/ˈlɪɡnɪtaɪz/Definitions
1. verb
to convert into or resemble lignite, a soft, brownish-black coal, or to give a lignite-like appearance to
“The ancient trees had begun to lignitize over time, their wood decaying into the earth.”
2. noun
the process or result of converting into or resembling lignite
“The lignitization process occurs in various types of organic matter over millions of years.”