It is a gas fire pit

What stone or is it black stone covering the gas?

Here's an idea that you could place directly on top of that rock -- Artistic Steel Logs. Will greatly warm the area around the outside for those seated. I'm attaching a picture of a fire pit that looks very similar located in Lake Tahoe, CA. Owners used to have lava rock and now are ecstatic with the outcome with our logs.

Jamie
rmironworks@me.com

It is black glass.....

gas fire pit

Beautiful