fossil

n. 1 remains or impression of a (usu. Prehistoric) plant or animal hardened in rock. 2 colloq. Antiquated or unchanging person or thing. attrib. Adj. Of or like a fossil; antiquated.  fossilize v. (also -ise) (-zing or -sing). Fossilization n. [latin fodio foss- dig]

a. Dug out of the earth; as, fossil coal; fossil salt.