fossilized

fossilized adjective
also British fossilised /ˈfɑːsəˌlaɪzd/
fossilized
adjective
also British fossilised /ˈfɑːsəˌlaɪzd/
Britannica Dictionary definition of FOSSILIZED
1 
: having been changed into a fossil
2 
disapproving : very old-fashioned and unlikely to change