lithify
[ lith-uh-fahy ]
/ ˈlɪθ əˌfaɪ /
verb (used with object), lith·i·fied, lith·i·fy·ing.
to change (sediment) to stone or rock.
verb (used without object), lith·i·fied, lith·i·fy·ing.
to become lithified.