Large square piece.

[planeguy2]

Is this an artifact of some kind? Found in a creek in Pa

[antmike915]

My first impression is that it's a natural rock, have you found any obvious artifacts and/or waste sherds in the area you found this?

[planeguy2]

I haven't found any, although I am not around there much.

[gregszybala]

Lintel or capstone or limestone brick?
Could be a petrified brick of Velveeta cheese?

[Hal Gorges]

Stranger stuff has happened in my fridge...Sorry plane guy, i love ya... I like those mystery pieces, can’t figure what that one is.

[paohrocks]

Agree with Greg.

[flintguy]

I think Greg might be on to something. It reminds me of old flagstone curbs. In someplaces they used to cut long strips of stone like that and lay them as curbs, before concrete became more popular. Better pics in the daylight might help. I would guess old construction piece, but I'm not sure.

[flintguy]

Still make them today.

[flintguy]

Look up yellow kerbstone.

[SurfaceHunter]

Both natural the flat one if it's the same type I find in a creek form like that and can be harder than a brick. I brought one home and it's hard for being so thin.