my first thought was a broken piece of drywall. but then i thought it's probably some english biscuit i'm not familiar with. here in texas, it would be a torn piece of tortilla. :)
You have beaten me. It looks a bit like a communion wafer but my memory is a bit hazy.
I don't think this right, but my best guess is the broken shell of a hardboiled egg.
I'll have another go. It's a piece of Styrofoam. This could go on all week.
Thank you for visiting. Hope you enjoyed the pictures. Any comment, or correction to any information or identification I get wrong, is most welcome. John