Philistine
backed
calcified
callous
calloused
case-hardened
crusted
crusty
crystallized
flinty
fossilized
granulated
hard
hardened
hardhearted
hornified
impervious
incrusted
indurate
indurated
insensitive
inured
lapidified
ossified
pachydermatous
petrified
proof against
reinforced
rigidified
sclerotic
set
solidified
steeled against
steely
stiffened
stony
strengthened
thick-skinned
toughened
vitrified