What Type of Rock is This Odd Beach Find from Northern California?

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The rock found on a Northern California beach is likely a type of conglomerate or breccia. If the included pebbles are rounded, it is classified as pudding stone or conglomerate. If the pebbles are varied, it is identified as polymict conglomerate. In cases where larger fragments are jagged, the rock is categorized as breccia. The possibility of it being man-made concrete from early construction is also considered.

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I need help in figuring out what type of rock this is. I found it on a beach along the coast of Northern California.
 

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Honestly, looks like concrete (after some rounds of rolling around).
 
Welcome to PF.
Maybe man made concrete from early construction industry.
Pudding stone or conglomerate if the included pebbles are rounded.
Polymict conglomerate if the pebbles are different.
Breccia, if the larger fragments are jagged.
 

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