Ancient beach!

[Rockboss73]

I found it in central Mn it’s petrified the white pieces can’t be picked off by hand. Please help thank you it’s about 14x4 3 inches thick..thank you 

[Kane]

I was going to say possible breccia/conglomerate/coquina, but the flakes don't seem to have any plications to indicate broken brachiopods. This is an odd piece, and I wouldn't rule out that it could be human made. 

[Tidgy's Dad]

Yes, it looks at first glance to be from a high energy environment where all the shells have been smashed to pieces and preserved, but on closer inspection the little pieces look too smooth to be organic.

Interesting. 

[goatinformationist]

I spend a lot of time with minerals and I can't place it.

[Walt]

A long shot here.

There is a type of concrete construction known as Tabby.  It uses oyster shells with the ingredients for concrete and looks something like this:

It was popular in colonial days, mostly in the south east, but has enjoyed a resurgence of late.  The shells are apparently burned or heated prior to their use and was popular because there used to be huge piles of shells available from Native Americans consuming fresh and salt water shell fish.  Like I said, it is a long shot, but I wonder if this was someones experiment with Tabby concrete.  The OP does not say what he or she thinks the matrix is, but it at least resembles concrete in the pictures.

If nothing else, here is a very interesting article about tabby concrete.

http://atlantapreservation.com/buildingmaterials/TabbyInfo.pdf

 

[Rockwood]

Cystoid crush ? Some of the angles look right. 

[Miocene_Mason]

Strange coquina look but not something I would expect in MN...