What kind of rock is this?

[coop626]

This is a rock my son found, having a hard time identifying.

 

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[Icewing]

Welcome to T-net, it looks like a concretion from here.

 

[relic lover]

Or concrete

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[P.ALLEN]

yeah it looks like a coquina of marine fossils, just like at the beach, that area between the surf and the sand is always loaded with crushed shell n other stuff, that's probably what it is...or..old concrete

 

[coop626]

Thanks for the help and after looking up concretion it is possible that's what it is...It is very hard and heavy for a rock no larger than what it is