Out of Curiosity (heh), where did you get the info that these are pieces of a comet, as the photo captions only call it “Rocknest”, and could be the result of many causes?
Well yes, but is is a perfect match for the “Thunder-smitten Thunderbolt” as described in Roger Williams book “A Key Into the Language of America” which was published in London in 1643.
Also, people with metal detectors collect it out in the areas around Cape Cod.But your right, the only absolute way would be to get a sample and analyse it.
Anyhow, it is not chondrite http://search.aol.com/aol/image?q=chondrite&s_it=img-ans&imgId=B43F0C0D5C3959A863AB42175D5A29F8FEC0DFFF&v_t=TB20