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

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The rock found on a Northern California beach resembles concrete and may be man-made, potentially originating from early construction activities. If the included pebbles are rounded, it could be classified as pudding stone or conglomerate. If the pebbles vary in type, it may be identified as polymict conglomerate. Conversely, if the larger fragments are jagged, the rock could be categorized as breccia.
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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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