fragment vs clast

fragment and clast both are nouns.

Word	Noun	Adjective	Verb	Adverb
fragment	Yes	No	Yes	No
clast	Yes	No	No	No

As nouns, clast is a hyponym of fragment; that is, clast is a word with a more specific, narrower meaning than fragment:

fragment (noun)	clast (noun)
a broken piece of a brittle artifact	(geology) a constituent fragment of a clastic rock
an incomplete piece
a piece broken off or cut off of something else

fragment (verb)	clast (verb)
break or cause to break into pieces