This page -- http://www.amsmeteors.org/fireballs/faqf/ -- suggests that it's very unlikely to find cometary-origin meteorites, even though the majority of observed meteors are cometary in origin, because the latter are too fragile to survive all the way to the ground:
Based upon photographic fireball studies, cometary meteoroids have
extremely low densities, about 0.8 grams/cc for class IIIA fireballs,
and 0.3 grams/cc for class IIIB fireballs. This composition is very
fragile and vaporizes so readily when entering the atmosphere, that it
is called “friable” material. These meteoroids have virtually no
chance of making it to the ground unless an extremely large piece of
the comet enters the atmosphere, in which case it would very likely
explode at some point in its flight, due to mechanical and thermal
stresses.
It goes on to claim that cometary meteoroids make up about 95% of observed meteors, 38% of observed fireballs, and 0% of fresh meteorites. (Since a hypothetical cometary-origin meteorite would weather faster than meteorites of asteroidal origin, they would be even less likely to be found later, and so it's not surprising that the page says 0% of all known meteorites are of cometary origin.)
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