Looks kinda like a wasp nest.

Light makes it all the way through.

Petrified honeycomb?

This looks a lot like pieces of coral my family brought back from costa rica. Very cool find.

Neat. Where did you find it?

That's really neat, I've never seen anything quite like that

Looks like a piece of someone's catalytic converter

Yeah, that's a bit of coral

Fossilized coral! I found a piece like that on a beach in Florida once.

Awesome rock!

Somehow this doesn't set off my trypophobia.

Urgh...

Trypophobia trigger

I've seen ceramic in industrial applications that kind of look like this, but I'm not seeing any pores in the material though.