tufa
volcanic rock
tufflava
breccia
clay-slate
clinkers
crushworthy
crystallites
culm
dubstep
ejecta
etz
felspar
grump
heer
laminae
lava-flood
off-kilter
porphyry
pumice
scoriae
shcool
weight-lifting
zeolite
Slough
bluff
bruff
buff
cuff
duff
enough
fluff
gruff
guff
hough
huff
luff
muff
pluff
puff
rebuff
rough
ruf
ruff
scuff
shuff
slough
snuff
stuff
tough