13th

and

anthracite

because

beds

black

brownish

called

can

carbon

century

coal

col

combustible

elevated

english

exposure

forms

fossilized

from

harder

has

later

layers

meant

metamorphic

mineral

occurring

old

pressure

regarded

rock

seams

sedimentary

since

strata

such

temperature

term

the

usually

veins

which